New to opks

ladies I am new to opks. I have a clearblue digital that I've been using for 3 months and never got a peak. so this month I decided to do opks with it. I got my first high on my clearblue digital this morning. I also did and opk. it had a line but not as dark as control. My question to you is how often do you check with opks and when do you start? should I do morning and afternoon since I don't know when I ovulate and never received a peak on my monitor? Glow says today is my first fertile day any help is appreciated.