Yes you can use diaper rash cream everyday if you want too.
It's a good idea to apply diaper rash cream to your baby everyday to help prevent a diaper rash because it's much better to protect your babies skin from getting diaper rash in the first place instead of trying to treat diaper rash after it happens.
Diaper rash occurs due to contact with the urine and feces from the diaper when the baby is wearing the diaper.
So by keeping the babies skin dry and protected against that wetness and poop it helps to prevent the diaper rash.
Diaper rash cream should always be used at night or anytime when the baby will be exposed to wet diapers for a prolonged period of time when you can't change the diaper right away.
You can also use some Vaseline to help protect the babies skin against wetness and change the diaper every 2 to 3 hours to keep your baby clean.
If the baby poops you should change the poop diaper within 10 minutes of noticing.