How to make cubemaps for my map

I’ve been woundering if there is a way to make a cubemaps for like, the lens on the crossbow, how can I do that?

Place some env_cubemap’s in the map and compile, make sure you type in the console “buildcubemaps” after placing the cubemaps too. If you have HDR in your map you WILL need cubemaps in or you’ll see white crap

you won’t need to build cubemaps for HDR, but you will need to build cubemaps twice if you have HDR.
First in LDR mode and then in HDR mode.