If you bought a station pass, then yes, you can play both EQ2 and EQ1 on the same account. If you didn't buy a station pass, then the answer is no.
You would go to the EQ1 web site ( http://eqlive.station.sony.com ) and download the patcher, then start the game download. If you don't have a fast internet connection this could take a long time.
You should really consider buying the game in the store just for speed of install, but you don't HAVE to, as far as I know.
Good luck. Frankly I think its too late to be starting EQ1, its very hard to play at the low levels because you are all alone most of the time. There's very few people joining these days. Unlike EQ2, where there's tons of people to play with.