First you gotta cut your beat to be able to stretch the beat: Use the blue tool button cut.
Also, set your ceiling to Cell as you see in the middle top.
Then cut from top to down on a beat, that is also set to its tempo.
Now make the track unique or the sample of your choice, so you can edit it:
Double click on the beat or sample and choose e3 generic or e2 generic:
To be able to stretch the sample you have chopped you need to set the STRETCH on with a button.
Then you need to drag the end of the sample in the playlist. While you drag it out, making the beat longer at the end tip of the sample, that way you will make the beat longer. As well it will most times play longer at the end. Somehow Resample choice in the sample isn’t quite the best option, as it will pitch the track.
The end is at this position; You just push mouse button on the end and drag it out.
Tip: There is an option in the sample that you can use besides using the drag out; Something like TIME and you can adjust it to find right time position of the chosen sample.
Tip: You can chop the beat up, just remain the time length of the beat at same position, that away you can edit the beats you purchased. If you need beats a great place to buy is: www.wonderousbeats.com