They are talking about checking toe-in. So if you were looking down from above your truck the tires would look like this \------/, only not that exagerated. I don't know what the spec's are for your axle, but you want the fronts pointed in a little.
I've checked this by putting a piece of tape on the front of each tire and drawing a cross with a marker on each piece. With the front axle on jackstands, measure to the center of the hubs. Now go back to your pieces of tape and put the horizontal of the cross at the same height as the center of the hubs. Now measure the distance between the vertical lines between the two tires.
Now rotate the tires to put the tape on the back of the tires. Measure the same center of hub height to the horizontal line. Now check the distance between the vertical lines again. The distance at the back of the tires should be larger. Not by much IIRC, like around 1/4".
This isn't the technically correct method of checking toe-in, but it'll give a good idea about if it's correct or even close. I've actually set mine this way and it seems to work just fine, but like I said it's not the most ideal method but it's the easiest IMO.
In order to get the steering wheel straight again, just adjust the length of your draglink. It's that simple. Most likely it's off because of additional suspension lift and you need to adjust the draglink anyways.