Generate navmesh

I just started with unity a couple days ago, can’t figure out how to generate a navmesh for my map. I got a grid working with a seeker but with 20+ units on a bigger map the pathing is too slow. The navmesh grid looks like it will be faster, but I don’t know how to create one for my map that will take into account obstacles (doesn’t need to be dynamic, just want to make one before I start the game). Can this be done with the free package? I don’t mind paying for the full version, just want to make sure this can run fast enough.

With the free version you need to generate a mesh in an external application, only the paid version can do that automatically.