To record or "render" the drum beats in groove agent, follow these steps.
Open groove agent
Find a groove you want to capture
Set the Left and Rght Locators (In the time ruler on the top of the arrange window) to the amount of measures you want
e.g. 16 Bars.
Go to File menu
Export audio mixdown
(select the format (Wave, MP3 etc)
Select the sample rate e.g (44.1) Bit depth e.g. (24-Bit)
Check the "Import to audio track" Box
Name the file and hit Save!

Done.