Hi Sharon! Assuming that level one is the easiest try this 40 minute random interval workout.
Warm up on level 1 for two minutes, then level 2 for two minutes, and level 3 for four minutes ( so warm up totals 8 minutes).
Now go to level 4 and ride fast for two minutes, and drop back to level 2 for active recovery for one minute (3 minutes total).
Then go to level 4 for three minutes at a quick pace and then bump up to level 5 for 30 seconds at your fastest pace, drop back to level 2 for active recovery for two minutes (5 minute 30 seconds total).
Now go to level 5 at a quick pace for one minute(if it bothers your knees, lift your butt off of the seat while you ride)now bump right to level 6 for 30 seconds at your fastest pace. Back to level 5 for a quick pace for one minute and then drop back to level 2 for a one minute recovery (3 minute 30 seconds total).
Do level 6 for one minute as fast as you can. Recover at level 3 for two minutes at a moderately fast pace (3 minutes total).
Do a high level that makes you HAVE to stand up to pedal at the fastest pace you can (it will be considerably slower since it is hard) for two minutes, drop to level 4 for two minutes pedaling super fast, the increase to level 6 and pedal at a quick pace for one minute and then drop to level 2 for a two minute moderate pace (7 minutes total).
Do level 3 fast for a minute, level 4 fast for a minute, level 5 fast for a minute, level two for two minutes at a moderate pace (5 minutes total).
Do the hardest level you can at the fastest pace you can (rear out of the saddle) for two minutes, recover at level 2 for one minute and then go to level one and pedal for the remaining 4 minutes (gradually slowing down each minute)(6 minutes total).
Do a thorough lower body stretch when you finish.
Please keep in mind if reading this looks to hard or too easy, simply alter the levels of your bike to challenge your current fitness level.
Good Luck!