You can take the Vicksburg exit (No. 45) and turn right going north until you get to Highway 72. Then turn left going west and it will eventually merge with Highway 95 that will take you to Parker, AZ and then Lake Havasu.
Or you can go past the Vicksburg exit to Quartzite and take the Highway 95 exit going north to Parker and Lake Havasu.
The second way is a little easier drive but a little longer. You might only save 15 minutes on the shorter route.