It can be hard for a new RP to get attention because of the extremely active ones that fill up the front couple of pages almost immediately - quite a few of those ones are groups of people who've RPed with each other before, so they are more likely to join RPs made by someone they know or based on one of their previous RPs than a new one. However, you can put a link in your signature to your RP (banners often help attract attention), and maybe join an RP or two so you can meet some of the other active RPers in the forums. :3 I'm not sure what level you like to RP at, but there's a Semi-Lit+ RPers club (
viewtopic.php?f=39&t=86636) where you have a good chance of finding people interested in joining new semi-literate or literate RPs.
Since there are so many RPs relative to the number of RPers, it takes a fair amount of luck for a new RP to take off, so often your best bet is to join one that's already been made and you find interesting - if it can get a few players, it has a good chance of getting off the ground. A very popular thing right now is one-on-one RPs, too, where you have just one RP partner, or private RPs with just three or four invited people; a lot of people like that because it's easier to keep the RP going the direction it was meant to and you can handpick your RP partner(s). If that interests you, you can search for a 1x1 partner here:
viewtopic.php?f=66&t=142204