Place the ligature on first (saves many reeds from getting nicked this way).
Slide reed in (fat end first)
Align it.
When you turn the mouthpiece over and look at the edge of the mp, you should only see a sliver of your reed.
Ligature is entirely up to you. Many mouthpieces have a line that goes all the way around them. This is a good place to line up the lig's leading edge.
P.S. Make sure your reed is properly saturated BEFORE you play... It will blow easier.
As far as getting back into the swing of things...
1) Long tones, start at middle G (left hand 1-2-3), play that until you have control of the tone. Then move DOWN one note. Go as low as you can without BLASTING. Remember this should all be done in a mezzo piano manner. Keep the corners of your mouth back like you were saying "ewww".
2) Going up from middle G is the same thing. Slowly ascend. Do not go to the next note until the note you are on is in tune and sounds good.
Do this EVERY day and you will begin to see your embashoure start to re develop. The next thing will be to knock the rust from those fingers.
REMEMBER: Nobody will want to listen to what you have to say musically unless you have good tone... Fast fingers but a goose sounding sax sound will make people RUN!!!