How do i add terrain collider to my randomly generated terrain?

Im making infinite terrain based game but when i always want to try it my player just falls through the terrain, so i need somehow to add terrain collider to the terrain via script. Can somebody help me with that? thx

i guess https://docs.unity3d.com/ScriptReference/MeshCollider.html is the way to go.

I cant select only one mesh because there is infinite amount of chunks in my game, i cant see any tutorial on the internet

Just add a meshcollider to each chunk and every time you update a chunk also update its meshcollider.
Same way you do it with the meshfilter.