How to flip down the back seat

flip the 40 side forward, then release the seat back on the 60 side so you can get behind the seat. Place a small shaving mirror on the floor under the latch and use a screwdriver to push the latch up. After the seat released you find out that there were 2 latches on the 60 side, and the one over by the 40 side must have been caught on something. You should now open and close the seat a couple of times.

The second row is folded by first pulling up the rear of the seat cushion and folding up 'til it's behind the back of the front seat. Then the back of the seat folds down where the seat cushion was.

The third row seats have several levers that are numbered in the sequence they are to be operated. First fold the seat back down on to the cushion and then flip the whole seat up 'til it's vertical and latched.

This is described in the Owner's manual if you can find one.

You have to flip the bottom of the rear seat forward. There should be a strap to pull where the seat bottom and seat back meet. The seats will not fold all the way down with out flipping the bottom up first.

can you take out the bottom part of the back seat is there any clips in the front of the back seat may be ask your Subaru service center how the bottom part of the back seat un-clips and comes out.
you may find a you tube video showing how to do this

should be in the trunk where the back speakers are

by the picture it looks like a 2000 to 2004 yukon.
im assuming you are talking about the 3rd row seat?
if so yes it comes out, the instructions are numbered on the seat, 1, 2 3.
if you are talking about the rear seat, inline with the rear doors, they do not come out, only fold down

Open the back trunk, look near the top of the trunk, and pull the two black levers. They have a seat folding down symbol. That will release the locks to fold the back seat down.

Open the trunk, there should be a black button on the driver's sid; pull it out. Don't close the trunk lid as this will push in the button. On the rear sea, drivers side, there should be a leather loop, it might be hidde between the seat and the inside moulding, puul on it and the seat will release.

The rear seats have a pull strap located between the bottom cushion and the backrest of the rear seats used to disengage a lock to lift up the bottom cushion. The pull straps will only stick out an inch or so, or they might have fallen down between the seats and then you wont see them. Before you can lower the backrest of the rear seats, the bottom cushions have to be lifted up and forward out of the way so that the backrest may lie down flat. If your pull straps are not visible between the bottom cushion and the backrest, you may have to stick your hand between the cushions and feel for the straps. Once you find the straps, pull upward on the while lifting on the bottom cushion where the pull strap is located and the seat should tilt forward. Once you have manged to do this, the lever for the backrest is located on the top of the backrest. Just slide the lever and tilt the backrest to the desired position.

There is one under the passenger seat driver side. Flip up the seat and lift off the cover.