1.  Install rubber seal on windshield glass DRY -- soap here makes it more difficult.

2.  Install trim at this point.  Cal-Look seals don't have to worry about this.

3. Wrap cording (yellow nylon line used for laying-out foundations works but
any small diameter, strong cord will be okay) around the perimeter of the seal,
in the groove for the body, TWICE.  It's very important that you go around
twice, starting and ending at the bottom center of the windshield.  This gives
you two tries at getting the seal lip inside the body.  This step is also why
these are called rope-in seals.

4. Now smear the inside of the seal and the seal groove with a *little bit* of
dish soap diluted in water.

5. Now you need at least one other person to give you a helping hand or two. 
Two people are better.  Get in your car and get comfortable sitting on the gear
shift and/or e-brake handle (it's in the only way).  Have your first buddy put
the windshield in place making sure to feed you the loose ends of the cord.  
With someone holding the windshield in place and someone putting some pressure 
locally at the seal (could be the same person if they are quite nimble), slowly 
and carefully pull the cording out of the groove and into the car.  This should 
pull the inner lip of the seal over the metal flange of the body.

6. Continue pulling the cord into the car while the person on the outside 
follows along with you putting pressure on the glass locally where you are 
pulling the cord.  Don't worry if part of the seal slips back off since you 
wrapped the cord around the seal twice you get a second chance.

7. If you are lucky enough to get the seal on everywhere the first time around, 
CONGRATULATIONS!  Just carefully pull the rest of the cord out of the seal.  If 
not just go around again and pay particular attention to the areas you missed 
the first time.