Unspayed females will go into heat twice a year (every 6 months). The heat cycle lasts 3-4 weeks, but the bloody discharge will only last for the first 7-10 days. Get her some doggy diapers and panty liners during this time to keep her from dripping all over the house. Also do NOT let her outside unattended even for a second. A fence doesn't give her much protection -- male dogs will not think twice about digging under a fence (or climbing over it) to get to a bitch in heat, and some females become "escape artists" when in heat. It would be best to keep her inside for the entire 3-4 weeks except for short potty breaks in your yard. Male dogs can smell a bitch in heat for miles, and you'll have them lining up at your door if you leave her out for too long.
About 2 months after her heat cycle would be a good time to have her spayed.
How old is your male puppy as of now?