1. Login to AdWords account.
2. Go to "Campaign Summary" under the top navigation tab that says "Campaign Management".
3. Click on the checkbox next to the Campaign you want to schedule.
4. Click on the "edit settings" button.
5. On the "Edit Campaign Settings" page scroll down until you find "Ad scheduling" under the "Scheduling and serving" section.
6. Click on the "Turn on ad scheduling" link.
7. You can see the days of the week listed next to which are the run-times, edit link and hourly schedules broken into groups of four hrs.
8. Click on the edit link of each of the day and set the right day and time you want to run your ads.
Hope it helps.