Your record label's promo people will send copies of singles/ albums out to friendly radio stations who will decide whether or not they play them.
Or you can do it yourself - take a bunch of press packs complete with copies of your CD and go visiting. There's still no guarantee of airplay
I might have the timings wrong on this bit, but I'm sure the PRS/ MCPS collect royalties from the stations every six months based on submitted playlist returns, work out what's due to everybody and pay it across - it's not a speedy process.
"Be good at what you can do" - Fingerbanger
"I have always felt that it is better to do what is beautiful than what is 'right'" - Eliot Fisk
Wedding music and guitar lessons in Essex. Listen at: http://www.rollmopmusic.co.uk