Okey doke - the next step is to remove the trigger assembly. First, you need to close the action, which you had to open in order to get it out of the stock. Use care! One good way to do this is to firmly grasp the barrel and slide (the part that goes around the magazine tube, and connects to the bolt) in your left hand and release the bolt with your right hand.
The bolt release, which Ruger calls a lifter latch, is that thing on the bottom of the receiver, just forward of the trigger guard.

(You should NEVER allow the action of a semi-auto firearm to slam forward, except when you're chambering a round. When chambering a round, AlWAYS let it slam shut from its rearmost position.) Then, ease the slide forward until the bolt is closed.

Before you proceed, put the safety in the safe position. Make sure no red is showing on it. The reason for this is that you do not want the hammer to be suddenly released when you have the trigger assembly out of the gun. That is a good way to damage things, including yourself. So don't do it. Put the safety in the non-firing position.

Now, see the photo. It shows a pin punch pushing the cross pin out of the rear of the receiver. This pin is usually not a particularly tight fit, and can be easily pushed through from either side.

Once the pin is out, move the entire trigger assembly rearward about 1/8", and it should easily come free of the receiver.