I found this answer and a comment under the answer also had the same question regarding parameters, so I am posting the solution here since the issue is slightly different and that question has an accepted answer.
First off, I installed powershell on the mac using these instructions and I modified the shell script task to include the Visual Studio Team Services (VSTS) environmental variables that I wanted to pass to the powershell script.

Next, I pass the arguments through to the called powershell script by slightly modifying the shell script mentioned by the referenced answer.
#!/bin/bash
powershell ./Version.ps1 $1 $2
Finally, in the powershell script, I catch the arguments that have been passed through using using param like this:
param([string]$version, [string]$path)
Wherein I can now use the variables $version and $path which contain the original arguments entered in VSTS to the needs of my powershell script.