I have purchased several "Products" for MT4 and been unable to transfer them to another MT4 Platform on the same computer. The rules state that there should be 4 other installs possible.
What do I do to really use those 4 installs? Likely I should sign in to my MT5 Account--but what then?
The 4 other installations means 4 other computers.
On each of these computers you can use the purchased tools with as many MT4 instances you like.
Below you'll find the official instruction video "How to reinstall market products"