A dominant seventh chord (often just called a 7th chord - C7, Bb7 etc) is created by adding a minor 3rd on top of a major triad. Here are some common fretboard patterns for playing dominant 7th arpeggios. However, these are not the only ways to play 7th chords. As with everything you learn, you should constantly experiment to find other ways to play each new chord type.
Dominant 7th arpeggios are commonly used when playing over Blues changes. Run through the basic progression first using arpeggios starting on the root note and then try improvising with the notes of the arpeggios, as shown in this solo in the key of Bb. Learn the solo, analyze all the chord tones and then transpose it to all other keys, as well as finding other fingerings for all the lines.