Frontier Airlines Code?

[PinkTink63]

After months of pain staking hours trying to find flights, I'm going to book our partial flight on Frontier. We usually fly Alaska, but the flights are outrageous this year!
I went to book our flight on Frontier and because we have not flown with them for more than two years, I have lost all of our thousands of miles accrued! I guess I have to sign up again for their Early Returns. I was noticing that it asks for an incentive code.
Does anyone know about this and where I might be able to find one?

Thanks!