Both Clairol and L'Oreal have customer service numbers you can call to get help during the bleaching process. The numbers should be on the box or in the instructions. L'Oreal may answer the phone in French, but don't panic, Anglophones. As soon as you start speaking English, so will they. You may have to bleach several times to get a colour as light as you want, and then work with some colour dyes to tone down the results.
Chlorine can cause bleached hair to turn green.
So don't go in a chlorinated pool without a bathing cap. You'll want to condition, condition, condition after bleaching. But the only real way to get rid of bleach damage is to cut your hair. The peroxide can be very strong. If you insist on using peroxide on your hair, make sure you use the right type.