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Dominant 7th chords are named by the root of the chord followed by "seven". For example, a chord (E - G# - B - D) would be called an E7 (E-seven) chord. Bb7 would be Bb - D - F - Ab. Any dominant 7th chord would be spelled by beginning with a major triad and adding the minor 7th above the root. One could also arrive at the 7th by naming the note that would be a minor 3rd above the fifth of the major triad.
In much the same way that a V chord can proceed to a vi (or VI in a minor key), the V7 chord can also go to a vi chord. In doing so we, once again, first resolve the tritone. In the example below, the tritone (F# - C) is resolve with the 7th of the chord (C) resolving down to B and the leading tone (F#) going to the tonic. The other voice goes opposite the bass (sililarly to the V - vi) to the doubled 3rd of the chord. Reiterating for emphasis, the tritone is resolved first.
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If you still have questions, contact Dr. Bartolotta at wbartolo@odu.edu.