A good way to start is with yourself and what you know.Dates and locations of birth, baptism, marriage, death and burial are helpful because that helps you identify resource material for those geographical areas and time periods of interest.Family Tree Maker is a good genealogy software program availabe in computer accessory stores for $50 to $75 depending on the kit you buy.
Working back from yourself, identify your dad, mom, grandparents on both parents side, and keep working backwards.
It is easiest to work from yourself backward in time with known information than it is to pick a progenitor and work forward.
There were several Perthuis families in France/Quebec in the 1600s I believe.
I have done some family tree work on my Perthuis line.
Knowing what French culture populations to search would also help, especially if you see that your family is from those areas:In U.S., midwest such as Illinois, Indiana, Missouri, northern such as Wisconsin, Michigan, Minnesota, east coast such as Vermont, New Hampshire, Rhode Island; west coast such as Oregon and California.