Most important things you should keep in mind ist that the 'closed' side of the seals should point towards the plastic ring in the middels. After the housing is emptied you should install the first seal with the open side not visible, so the closed side up. I use vaseline to lube the inner 'lip' before installing. This lubrification is meant to guarantee a correct fit of the lip around the axle that is positioned later.
After you pressed the first seal totaly into the housing of the water pump, you add another good quantitee of vaseline and please do force some of it from the inside through the tiny hole that is meant to warn you when one of the seals starts leaking.
Now it is time to get the plastic distancing ring in place. Again I add another good quantitee of vaseline on top of this ring.
Third step is to get the second seal into the water pump hougin. Please grease the lip of this seal with vaseline as well before installing. Now push the seal in position with the 'closed' side towards the inner plastic ring.
Step four would be the installation of the two new outer o-rings. It is unwise to re-use the old ones as leakage is almost a certain result... With the two O-rings in place it is time for
Step 5: get the axle with impellor in position. If your vaseline is a little like mine, the tip of the axle will be showing some residue of vaseline. Just wipe it off and your water pump assembly is ready for use.
You will find additional photos through the link below. It is in German but the graphic material is useful nevertheless. Also you will see that the deeper positioned seal can be pressed in place with a socket (from a wrench tool kit).http://www.guenther-nds.de/c1tech/wasserrepsatz.htm
Many greetings from the flattest country of all Europe,