From Worms Knowledge Base
The latest version of Worms Armageddon is 3.8.1, released on 23 December 2020. You can check your current version by placing the mouse cursor over the "Worms Armageddon" logo in the main menu, and checking the text at the bottom.
Obtaining the latest version depends on your edition (the format in which your purchased WA):
All updates for the CD edition of the game are listed and downloadable from the updates page.
Steam / GOG
Updates for the Steam and GOG editions are distributed through Steam and GOG respectively. The game launcher software (the Steam client / GOG Galaxy) will usually keep games up to date; or, in case of GOG, updates may be provided for download separately.
Note that it may take some time for updates to be published on these platforms, as they need to pass through their respective release processes.