I try and open a AE file template for an intro, but it says it was created in a later version. How do I update after effects?
Nobody can tell you anything without exact system info or other technical details like the exact version of AE you use and which version the template requires. That being said, AE files are simply not backward compatible and you may simply have to ditch the idea.
It depends what version do you have. If it is CS6 or earlier - you have to buy Adobe CC subscription Adobe CC Plans or if you already have CC subscription you have tu update your AE using Adobe Creative Cloud app.