Adjusting a double set trigger is a simple task with no pitfalls.

The screw between the triggers is all you manipulate.

before doing anything MAKE DAMN SURE THE RIFLE IS UNLOADED.

As stated above, this screw must turn freely and should not be forced. If your's won't turn, try a little penetrating oil first. Don't use too much so as to allow the oil to contact any wood. Let it soak in while lightly tapping the adjustment screw. It should free up.

If that doesn't work, try a little heat from a soldering iron. Just apply the hot soldering iron to the head of the adjusting screw until it gets pretty warm. Then let everything cool off and try to turn the screw. Don't try to turn it while hot, as you have the screw hotter than the surrounding metal, which actually makes it tighter. Once it is cool it has contracted back to size and should turn. If it doesn't, try the penetrating oil again.

Once the screw will turn, you're almost home, and certainly at the fun part. Have no fear from this point on.

To adjust the screw, again MAKE DAMN SURE THE RIFLE IS UNLOADED. This can be done with the rifle uncocked or even with the bolt out of the rifle (assuming it is a bolt gun). Set the triggers. Then turn the screw clockwise (in) until the set trigger releases. In your case, this isn't going to take much. Pay attention to how much of a rotation it takes to release the trigger. Quit turning as soon as the set trigger releases.

Now back the adjustment screw out (counter-clockwise) about one full turn. This increases the engagement of the tiny sear between the set trigger and the firing trigger. Set the triggers and give it a try. If you like it, you're done. But you may feel some "creep" in the letoff of the set trigger, in which case you need to turn the adjustment screw a bit tighter (clockwise) to eliminate some of the engagement of the trigger sear. Keep trying and turning until you have exactly what you want. In my experience somewhere around 1/4 to 1/2 turn from letoff is good. This is something you can try till your heart's content. You are hurting nothing. Remember, your baseline is where the set releases, and you work back from that point.

I do not recommend putting loctite or sealer on the adjustment screw after adjustment. Generally this screw will not turn on its own. You want to be able to adjust this screw from time to time to suit your fancy.

That's all there is to it. Nothing fancy and no rocket science. Your biggest problem is getting the screw to turn without buggering the head of it.

A single set trigger adjusts the same way also. This is not a spring adjustment. Normally the spring cannot be adjusted at all. You are adjusting the sear engagement between the set (rear) trigger and the letoff (front) trigger.

Good luck,
Curl