The Audit Log has been available in all versions of Skyline since 2018.
If audit logging is not currently enabled in your Skyline document you can turn it on by first using the menu item:
View > Other Grids > Audit Log
and then checking the checkbox that says "Enable audit logging".

There is some more documentation about the audit log here:
https://skyline.ms/wiki/home/software/Skyline/page.view?name=audit-logging
-- Nick

Thanks, i saw the pdf on audit logging before but was not sure how to enable it. I can see it now. Is there any time frame to how far the audit log goes back, or will it just record all actions on that project?

No time frame. It will record all the actions since the moment when the audit log was enabled.