Yes I need help trying to connect p trap from my mobile home to my septic tank.if anyone has some advice that would be nice.

P-traps should already be under every sink and toilet in the home. All lines from the p-traps should be straight graduating lines to the main line that leads to the septic tank.
Look under your sink if there is a pipe that looks like a has a dip and runs striaght to the wall that's a p-trap. Most toilets come with this built it.

In hind sight if u need to put a p-trap in u can use a slip p-trap near the outside of the house as close as possible for less digging.find out what size discharge line u have 3 or 4 inch.