How To Beat Match Songs
Beat matching is a process of taking one or more songs and matching up their beats and adjusting their tempos so that the beats stay locked through the transition.  This example shows how to take two songs, beat match them and then increase the tempo from 107 bpm to 119 bpm during the transition.

We are going to mix Atomic Dog by George Clinton with Beds Are Burning by Midnight Oil.  We've loaded in Atomic Dog and the software has detected that the tempo is 107 bpm.  Click on the Sound Details Tab to look at the sound's detected tempo.

Next, we load in Beds Are Burning so that we now have two songs in our project.  Notice that the project's tempo is still 120 bpm.

We change the project's tempo to 107 by either going to the Project Details Tab or by right clicking the first marker and choosing Edit...  (we've highlighted the new tempo in red).

Zoom in on the transition and move the sound Beds Are Burning to start on the last major beat of Atomic Dog.

We don't want Beds Are Burning to play at 107 bpm because its normal tempo is at 119, so we add three tempo markers that ramp up the tempo during the transition.  Add a marker by double clicking the time line or right clicking the time line and selecting Add Marker...

That's it!  Add more songs, add more tempo markers and burn it to CD or mix it down.