Just execute the setup file you downloaded and follow the instructions on the screen.If you are upgrading from n older version please stop any running Winslew instance prior to start the installation.
Enter your existing Pocket credentials into the setup window or create a new account right in place. If you already entered this data successfully on a prior start of Winslew this window is skipped upon startup. You can open the settings manually by pressing the preferences button on the main window: 
Next Winslew reads the stored hard-disk cache (if available).
After the initial cache fetching is completed you get the main window with your reading list
In case you are starting Winslew for the first time or you have added new items to Pocket since your last start of Winslew the cache for those items is being created. You can see the progress of the cache update on the bottom of the main window. Hint: The progress bar will run twice for all items as in a first run the more and less views are created while on the second run the full view is being created.
On top of the main window you find the main toolbar. This toolbar includes the following buttons:
Refresh: When pressing this button a new sync with Pocket is initialized and if you added new items they will be added to the Winslew view list
Toggle view: Change the view of items Read items <.> Unread Items
Change title: Change the title of the selected item (this is synchronized to Pocket)
Edit tags: Change the tags for the currently selected item
Add tags: Add tags to one or more items at once
Remove tags: Remove tags from one or multiple items at once
Change read state: Mark the currently selected item read or unread according to its current state
Add item: Add a new item to your Pocket list. A new window will be opened to enter the URL of the item
Upload image to imgur and add it to Pocket (see below)
Store a text online at Pastebin (see below)
Upload a local text to Pastebin (see below)
Delete item: Remove item from Pocket and Winslew
Preferences: Open the preferences for your Pocket account and licensing
About: Get some information about the installed version of Winslew
You can filter your list for the content of the title or the tags. Simply enter some characters into one of the input fields and see the list view changing dynamically
Within the title bar of the currently selected item find some view specific buttons
Add currently shown webpage to Pocket (only shown if not already in list)
Copy link. Copies the link of the currently selected item to the clipboard
Open in webbrowser: Opens the currently selected item in you default browser
Rebuild cache: Updates the cache for the currently selected item.
For the more and the less view (and only those) you can choose between styles for the display. As with Winslew 1.3 the following styles are included in the default installation:
You can define own styles easily if you have basic knowledge about Cascading Stylesheets. See the extra Style creation manual.
Hint: If you recently upgraded from a Winslew version lower than 1.3 the style switcher might have no influence on your view. The styles only apply to more and less caches which have been created or updated using at least Winslew 1.3.
Winslew comes with four different views included which can be changed using the dropdown menu in the toolbar
Online: Shows the webpage of the item online
Full: A view trying to fetch as many design elements from the webpage for offline usage
More: The more view is a text online view of the page trying to filter things like navigation and footer away
Less: This view trys to online show the real content of the page. If this view filters to much of the page try the more view instead
Since Winslew 1.5 you have the option to either send an existing text file or a self written text/copy&paste to the text storage service Pastebin. By pressing 
or 
you start the upload progress which will bring an editor window like this to front:
When pressing send the text is send to Pastebin and the resulting webpage will be added to your Pocket subscription. Please be aware that Pastebin is a public service so even when you choose post exposure to be private anyone who knows or finds the URL will be able to see your text. See the Pastebin FAQ for more information.
Since Winslew 1.4 you have the option to upload a local image to the image hosting service Imgur. The image will be uploaded to a public website (meaning anyone knowing or guessing the link can see it – so don’t upload any secret/private pictures). It is then automatically added to your Read It Later subscriptions.
To delete an image choose the more or less view of the item. Find there a link to delete the image from Imgur. See Imgur FAQ if you deleted the Pocket item before you removed the image from Imgur to get it removed there too.