I have an F5, great machine.
Go through the manual outside the house and practice with coins and nails and aluminum trash using the examples in the manual. Get familiar with how things are. (inside house is too much electrical interference and metals)
I'd set gain at 60, threshhold at -5, and be sure to ground balance it.
You can run all metal mode which runs deeper because the discrimination circuitry is not being used. Discrimination though allows you to tell it to ignore certain metals like steel nails. Problem there is jewelry and gold coins tend to come up the same as some trash you will get tired of digging. Number of tones is used with discrimination, if you get tired of one tone all the time, it will make one tone on a quarter, and another tone on trash, another tone on a penny.
Best advice I can give, is to go through the examples in the book using different coins and objects and get familiar with the all metal and discrimination modes. And practice "pinpointing" in your yard for accuracy and depth.
Depending upon the size of the object detected, the depth reading may be wrong because it is a large object and the discrimination circuitry is calibrated for coin size objects.
It takes two 9V alkaline batteries, buy good ones, and get some spares just in case.
Any questions, ask away, lot of F5 users here willing to help. There are no dumb questions, I've asked them all!