If you have lot of expense reports to approved, follow the below process to approve them quickly     - 

1) Go to your home page (Menu->Home). All expense reports pending your approval are present under the "Employee Expense Reports Awaiting Approval" section. Open the first report to approve as shown below.

2) Once you approve any report, to view the next report pending for approval, click on the "Next Report" link. This way you don't have to go back to the Home page to open the next report.

3) On click of the 'Next Report' link,  you will be presented with the next expense report pending for your approval.