Install and set up Gale or r2modman, whichever you prefer.
Switch your mod manager's managed game to Gang Beasts, and make a new profile if needed. You can look to the respective managers' pages for how to do this.
Click the blue Install with Mod Manager button just under the top info section of the CementGB Thunderstore page. This should install both CementGB and all listed requirements.
Start the modded game through your mod manager. You should be good. In order for anything to actually happen, however, you must install some content mods. Most can be found on Thunderstore.

Install MelonLoader as per their instructions on their README.
Download and extract the .zip from this page by clicking Manual download.
Extract the konradKG25-Airport-x.x.x.zip and move the Mods folder inside the extracted folder to C:\Program Files (x86)\Steam\steamapps\common\Gang Beasts
You should be good to go.

konradKG25 - Cinematic Animator

konradKG25 - Normal Map Creator

konradKG25 - README helper

striped_shirt_dude - 3D Modeling

striped_shirt_dude - Texture Designer

minimack_studios - Project lead

minimack_studios - Animation, collision, and overall refinement

minimack_studios - 2D Artist (Images for Billboards)

minimack_studios - Release package structure

minimack_studios - Cinematic Animator

rafa120hojaz - Cloud particle system creator

Sunshine Airport, from Mario Kart 8, composed by Atsuko Asahi - Music (NOT AFFILIATED)

Note: There is more to the credits, but it's too much to be worth writing out. Plus, who really cares?

konradKG25

ansondacool_69

minimack_studios

Thank you for vising Beast Airlines. Sponsored by BEEF CO.

Gang Beasts

Airport