You can download the 'compcon-ks-content.zip' file from the app page, extract it somewhere, then open COMP/CON > OPTIONS in the top nav bar > Import content package and select the extracted folder.
After that, you'll get a little toggle to turn on the long rim mechs
It's a little convoluted, and they're missing art, but there's an incoming rework to better accommodate expansion packages
oh sorry, I should have made a comment in this thread -- as of the last version, the Long Rim mechs have been pulled in to the core data. Now that C/C is official, from here on out the only stuff that won't be in the core data will be either homebrew stuff, or, separate future expansions/modules
