Sorry for the delay - but I think most people incorporate it into lessons as something the students are doing, without having special lessons for it. Through Code Studio you can have students select each other (from the Pair Programming menu in top right corner) and this way they will both get credit for the lesson, or - like I do - I have them work together and do it twice to become more comfortable with the code and sometimes there are errors they need to troubleshoot.
One of the most important things though about pair programming - which can be done on any unit, any lesson at any time - is that students don't switch off once they've finished a task - keep a timer for students to finish and try to make it a little random. If a student knows they won't be working on the project until the other student (or "driver") finishes the bubble, they will be checked out during that time. Make sure they are actively working together and can be called upon to switch roles (driver to navigator) at any time.
Let me know if that makes sense!