long press on the message(s) you want to delete and click the trash can at the top.

To empty the trash go to the trash folder, click menu, and select empty trash.

In the phone tutorials on the phone and online, I've seen info on setting up and deleting a gmail account, but nothing on how to select and delete gmail (i.e. delete all) or a portion thereof (i.e. via a shift feature). Also haven't seen any info on thereafter emptying deleted gmail from the trash bin. Any help would be appreciated...thanks.