I'm looking to upgrade my Desire 510 to lollipop but I have no idea how to go about it, or if it is even a good idea, would I have to root my device before hand?
Thanks
First, you dn't root, then update. Rooting roots the ROM. If you're going to replace the current ROM with an update, rooting the current one is a waste of effort. You'll have to root the update too in most cases.
Second, I doubt that HTC will come out with a Lollipop ROM for the 510 - it's too old.