how i do that i am triying to do it but idk how...

somebody can help me? like the basement on the map cabin

W1NG3D was the one who created the Cabin building in Radiant so you might want to wait for him to respond, but I'm pretty sure it's just a terrain patch with a default Treyarch spiderweb texture placed on it. I would send you a sample but I can't seem to find the prefab he made of them - I'm sure he still has it.

I just created some non-colliding vertical terrain patches with the default spider web textures from Treyarch, these can be found under Textures -> Usage -> damage (I think). Then I just made the patch a prefab and copied it around the basement to make the cobwebs appear thick.

Hope this helps