Recipe

1. Put Xamarin Studio or Visual Studio into Debug mode, and set a breakpoint at the point in the code where you want to start stepping from. Then, hit debug.

2. On the top left, you will see three green and gray icons with arrows. You have three options here:

Step over and Step into execute the next line of code. If the next line of code is a function call, Step over will execute the entire function and stop at the next line of code outside it. Step into will stop at the first line of code inside the function. Use step out if you are within a function, and want to move on to the next function. 

You can see we've stepped into the next function, which is SetMode: