.  C:\mydir\powershellfile.ps1

easy enough. The period in the front is like your include statement in other languages and YES there is a space between the period and the C:\. If your include file is in the same directory you can do a relative path like so

. .\powershellfile.ps1 (.<space>.\powershellfile.ps1)

notice the space! This is where I got lost. There must be a space between these periods. Do not if you want to autorun your powershell file relative paths usually want work. In order to do this you must create a .bat file that will execute your powershell file. When the .bat file does this the powershellfile is executing from the .bat location, or at least that is what I come to determine. So in order to get around this and make my life of managing these scripts easier I created a variable to hold the absolute path as such

$this_path = C:\mydir
. $this_path\powershellfile.ps1 #this includes the file with a absolute path

so far this is working great for me and should make it much easier if I ever need to move the script.