If you can't tell when they are ready, then you're probably not ready yet either. What do you know about breeding? And how old is the male you are getting? If it's not too old, then by the time it does mature, you'll be ready if you do the research.
Males - After their ultimate molt. They will have tibial hooks under their first set of legs and the ends of their pedipalps will become swollen like boxing gloves.
Females - Once they reach 75% of their adult size.
After your male matures, you'll want to wait a few weeks after your female has molted to breed it, that way she won't molt out of being gravid.