A problem with Add Force & Set Physics Linear Velocity related to independent framerate!!

Unfortunately, I’ve never done this before, I really don’t know where and how. I work exclusively with blueprints, I never touch the files or anything in C++.
The two files I need to create myself, like create a text document with .h and .cpp format and put them in D:\Project\Source\ProjectName with the code?
I don’t know about the build and compile part, do I just open the project or do I have to go into Visual Studio somewhere to build it?