When to start using OPKs

So, I just got my first period after having a D&C on May 30th. I’m very relieved because I’m 35 and I was afraid it would take a while for my cycle to return. My OB said we could try again after one cycle. I’m just wondering when I should start using the ovulation tests? We are really hoping to conceive sooner than later. I miss my little nugget and I can’t wait to take care of another baby. Hopefully we can make the next one work. We found out our nugget had Down syndrome. I feel nervous about everything, hopefully TTC will help with some of the emotions.