Moving From One Module To Another

I have code broken out between two different modules due to size limitations in a single module. I'm not able to figure out how to move to the second module after running the first module. I've tried something like this:

Sub FirstModule()
'Code
'Code
'Code
SecondModule
End Sub

Sub SecondModule()
'Code
'Code
'Code
End Sub

I'm getting an error that says "Compile error: Expected variable or procedure, not module". I understand that it's not allowing me to use the name of a module as a procedure, but I can't find any information on how to call the second module.