Firstly, decide what type of application you are building. If it's a basic console application that you're doing out of a textbook, choose a Console or Empty Project (probably the former). Most of the others aren't useful for learning purposes. You will need the Windows Forms project type if you later progress to GUI applications, or WPF for newer textbooks that teach that. The project type basically preconfigures your development environment with sane defaults and some auto-generated code (mostly includes and a stub for main, or an empty form for a GUI project). An empty project will simply give you a single blank file and require you to add references as you need them.
As for your second problem: There are two modes for running the project, Debug and Start without Debugging. The latter will automatically force the application to pause once it has reached the end of its execution and will sit there until you press a key. The Debug option will not do this. Since your program does not contain any line that tells the program to wait, it simply does its calculation, outputs the result to the console and then exits. The easiest solution is just to add a line that waits for user input.
Also, either Run method will first build the project before executing it, so you don't need to explicitly build and then run