I changed brake fluid reservoir and now it leaks from the rubber seals. How to get it tight enough?

Smear brake fluid on the seals and make sure they are fully seated.
Remove and discard the protection caps, smear the nipples with brake fluid and wiggle the tank into place.

Tomvw said:

Smear brake fluid on the seals and make sure they are fully seated.
Remove and discard the protection caps, smear the nipples with brake fluid and wiggle the tank into place.

Click to expand...

This exactly what I did.. Twice, but it's still leaking. Maybe I got the wrong rubber sealing...?

It takes quite a bit of force to push the nipples into the rubber bushings. Make sure the rubber seals and nipples on the plastic reservoir are completely wet with brake fluid.
Massage the plastic reservoir back and forth (repeatedly) until it snaps into the bushings. DO NOT use excessive force at extreme angles trying to get the reservoir into the rubber bushings. You run the risk of cracking the reservoir.

I've done this before as a last resort when I changed the reservoir on my 98 GLS the first time. It has the same type reservoir as yours.
Use a light white lithium grease in VERY small amounts (just enough to lube up the very tops of the bushings) and press the reservoir in.
You have to make sure you get ALL of the lithium grease out of the braking system. After a few days any of the lithium grease that got into the system will dissolve but then a brake fluid flush is highly recommended.