Hi everyone!

When I try to launch The Witcher 3: Wild Hunt, it opens in a seperate window but I'm not able to switch to it and commence the game.

Much appreciated in advance,

Cam

You should ask Kevin Bacon, after his work on Apollo 13 he might be able to help get it in orbit.

If you could provide any information whatsoever you may get more help. For example, some basic stuff:
What operating system
What computer - specs, do they fulfill the minimum specs on the game page
What errors to you get
How are you getting the game? Is it via galaxy, if so use the non galaxy exe located in the install location.
Make sure you install outside windows folders, maybe c:/games

This thread suggests running the game in full screen:

https://www.gog.com/forum/the_witcher_3_wild_hunt/after_update_gog_galaxy_the_witcher_loses_window_focus_on_the_game