Changing A Function To ASYNC or MultiThreading

I have a function in C++ and I want it to use ASYNC or MultiThreading because when it runs on the main game thread it freezes the game when it loads. Not sure what which one will be better but dont think it matters too much (ASYNC or MultiThreading). The only things thats changing in this function are in the file.
Thats how the function is setup in the header file under private:
void UpdateMesh();
I’m pretty new to C++ so if you can please give an example and a full explain on it it will be awesome. Thanks :stuck_out_tongue: