Determine what vocal style and lyrics will be the best fit for your dubstep production. Many dubstep tracks have reggae- or dancehall-style vocals; hip-hop- and R&B-influenced vocals are also popular. Think about the tone of your production, and decide which style of vocal works best with it. A vocal need not always be in a similar style to the production: contrast between the vocal and the instrumental can create a powerful effect. An ethereal female vocal part contrasted with a heavy, distorted bass track, for example, can sound great.
Record the vocal, or source it from a sample pack or vocal track. Recording yourself or a friend singing is the best way to create a unique dubstep track; however, if that's not possible, look for a suitable vocal in a sample pack. Audio companies like Loopmasters, Prime Loops and Producer Pack sell royalty-free dubstep sample collections that include vocal loops designed for use in this genre. You can also use the vocal track from another song; many single releases include an "a cappella" track that contains only the song's vocals. If you plan to release or share your dubstep track, make sure that the vocal's license allows you to do so. The ccMixter website hosts a collection of Creative Commons-licensed a capellas that you can use freely in your dubstep productions.
Integrate the vocal into your dubstep production. Open the project containing your dubstep track in your digital audio workstation, then add the vocal to a new track. If the vocal is out of time, enable your workstation's audio warping function, then stretch the vocal out so that it's in time with the beat. Cut the vocal into verse and chorus sections, then drag and drop them to rearrange them on the timeline.
Apply audio effects to the vocal. As in most genres of electronic music, the vocals in a dubstep production usually make heavy use of effects. Experiment with different reverb settings to add a spacey sound to the vocal, or add a bitcrusher plugin for a distorted effect. Equalize the vocal so that it fits into the track, then compress it so that it stands out in the mix. Export the entire project as an audio file.