In the game you find the setting under Settings → Keyboard/Mouse → Mouse Sensitivity.
The quicker way is the console: sensitivity 1.2
Conversion
Apex Legends to CS2 Sensitivity
In short: Apex Legends sens times 1. 1.2 becomes 1.2. For your own value, just edit the sentence below.
How to set it in CS2
What changes when you go from Apex Legends to CS2
Apex Legends and CS2 turn the same angle per mouse count. You can keep your number as it is.
The default field of view is almost the same: Apex Legends 105.5°, CS2 106.26° horizontal. The picture feels alike. For Apex Legends the field of view is only a rough guide, check it in the game.
In CS2 you can enter up to 3 decimal places. Use all of them to keep the conversion exact.
Common questions
How do I convert Apex Legends sens to CS2?
Multiply your Apex Legends sens by 1. 1.2 in Apex Legends becomes 1.2 in CS2.
Where do I set the sens in CS2?
Settings → Keyboard/Mouse → Mouse Sensitivity. Or in the console: sensitivity 1.2.
Why does CS2 still feel a bit different?
Apex Legends: Slider from 70 to 110 (about 105 to 106° horizontal at 90). CS2: 90° at 4:3, about 106° at 16:9. Match the field of view as closely as you can; then the converted sens feels most natural.
Does this also apply to scopes?
No. The values are for hipfire. Zoom and scope sensitivities are set separately in the game.
Should I change my DPI?
No. Keep your DPI and only change the sens in the game. That keeps your feel the same everywhere.