I am writing a Workflow script to get the Last Mod Date of an entry id and it wants to use a function called "LogMessage" How do I add the library that contains this function to Workflow?
I'm not sure what you mean by " it wants to use a function called "LogMessage"", that is not a function that Workflow uses. If that is from some 3rd party library, you can add that library as a reference from the References node in the top right section of the left pane (Project Explorer).
There are 2 way of recording messages during a script's execution. You can add messages boxes for testing the script from the Designer or you can use WorkflowAPI to record messages in the instance details at runtime. Look at the TrackInformation, TrackWarning and TrackError methods.
Protected Overrides Sub Execute()
'Write your code here.
MsgBox("This only displays when testing this script from the Workflow Designer")
WorkflowApi.TrackInformation("Hello World!")
WorkflowApi.TrackWarning("Warning! something unexpected but non-terminal happened.")
WorkflowApi.TrackError("Something really bad happened, terminating the script now!")
End Sub