Listen to R&B style music to get an idea of how the music sounds. Artists like Stevie Wonder, Aretha Franklin, Luther Vandross, Usher and Alicia Keys are good choices.
Buy a midi keyboard and a music software program that will allow you to record. Ensure that the keyboard is compatible with your computer. Start out with a midi keyboard with fewer keys if you do not play the keyboard. This will give you more control.
Install the software onto your computer and connect the midi keyboard. Open the music program and get a feel for how it functions.
Before you find your melody, set the tempo to about 90 beat per minute. R&B music is usually slower paced. Use instruments like strings, bass guitar and piano. These sounds are popular in R&B. Begin with a 4-bar intro. Make the chorus 8 bars and the verses 8 bars.
Top off your beat with a vocal sample. This will give it more of an R&B feel. Use a voice that is popular in R&B music.