How do you add a drain in a basement that does not have one?

its not easy but if you can locate your main drain pipe and its below your basement floor then saw cut up the floor and attach the floor drain to the trap and then tie on to the main line using the same pipe or adapters. If you have no main drain under your basement floor then you will need to saw cut a hole for a sump pump pit or basin and install the sump pump to your main drain line which has to be installed so your sump pump line runs higher then your main line before wyeing to the main line. then cut up the floor to where u want your floor drain and run the drain to your sump pump basin . Some states want a vent on your floor drain and on your sump basin so I would check what your local codes are.