To make your custom cmdlets (functions) available in your PowerShell sessions, there are a few methods.
To do a one-time import of functions in your current session, store the functions in a PS1-file and save it somewhere. Then, in your session run the following:
Notice the dot and a space behind it. This method, called "dotting" does a one-time import in the current session. This is useful for when you have functions that you don't use often, and don't want them to be available at all times.
An alternative method is to save the functions as a PSM1-file (extension .psm1) to create a module file, then use Import-Module to import your functions.