Laura:
A lot of people have made some good suggestions in regards to advertising, but it's not easy advertising with P411 or DC. Especially DC. For both sites you will need reviews and I believe you will have to have a website (it's one of the ways they verify). They need to verify that you are a provider and will not be able to do so without you having reviews. Yes, they are good sites to advertise with, but it is a process.
In my personal opinion, Date- Check is a lot harder to get approved by. Do start the process, but be patient. For P411 I found it to be a little easier after having at least 3 reviews.
I suggest you visit both sites and read there qualifications on being approved . Also, the internet is your best friend in this business. Google Escorts in Portland or whatever town it is you want to work and advertise in and see what advertising sites come up. Think about this what gentleman, who have never seen a provider, would do to see who what sites they should go to find providers.
BP is a low cost advertising resource to use, but be careful. Eros as well, but the could be expensive. Remember it takes money to make money.
Bottom line is always come and ask whatever questions you need help with on the Newbie Board, but do your own research as well, because there may be sites that are better for providers in Providence to advertise in than someone in (for example) the Chicago area
(which RS2Kis popular as well). In short, it's all based on the area you want to work in.
TER is GREAT place not only to advertise, but to ask questions such as the one you've asked. The Newbie Board is very helpful and friendly. There are A LOT of providers that will help you.
I've only been in the business 3 months and I have to say the ladies on here have been very helpful.
Good luck!
eom