She meant studying up about pregnancy prevention 
.
The best way to steer out of trouble would be studying your
cycle. Basically, your menstruation cycle is of 28 days and
ovulation occurs only 3-5 days in between the 28days, i.e 14(+-5),
so the 1-8th and 19th-28th day(23rd to 28th day where bleeding
occurs) are pretty much safer than the other days.
Of course there are variables(hormonal changes, stress, diet,
exercise, drinking) which affects the cycle, so it may not be safe
when you think it's safe. But serves as a guideline.
The period of time right after bleeding would be the safest, but
I limit it to a good 7 days only.
take note that not all every lady will have a 28 cycle.
some has short, while others longer. up to 31-32 days. so the
number of days in each phase may vary too.