How to create a title block?

Re-posting here as I initially posted my question in the wrong section of these forums.

Is there any guide on how to create a title block? I have been looking on the forums and googled it but I still have not found a clear explanation to do what I need.

I have inherited a title block that I would like to modify. When placed, the block auto-fills some fields, for instance the PROJECT, CURRENT PAGE and TOTAL NUMBER OF PAGES are filled and updated automatically, so that the block always shows "PROJECT= my project name", "PAGE YY OF XX" (where YY and XX are actual numbers.

Now, I naively copied the part using part-developer 17.2 and saved to a new library. This, alone, seems enough to break the nice field functionality and now the title block shows instead
"PROJECT= $PROJECT"
and
"PAGE $CURRENT_DESIGN_SHEET OF $TOTAL_DESIGN_SHEETS"

How do I fix this? What is the correct procedure to create those "magic fields"? And, more importantly, where is this all explained?

Many thanks in advance for any help.