tail light problems- HELP!

I have become very confused at my taillights. I have working turning signals and brake lights - but the brakelights, when it is night and i have lights on, do not run dim (rear running lights) so i have no rear lights until i press on the brake.
that is the cluster that is in the trunk.
the cluster that is attached to the trunk door is even worse. there are slots for 2 bulbs of the same size, the top one (that goes through to the orange light is in but I dont know what it is for.
below that bulb is my real problem. there is no bulb in this section - on either side. but he peice that clips off to put the bulb in accepts a big bulb. BUT when the bulb rack needs to be cliped back in the top orange bulb fits perfectly while the bottom one (for the red -running light) has a large plastic attachment on the back that prevents the bulb from fitting, so not only do i have no rear running lights, i have no way of fitting them.
Im very lost with this, i have found no help in the manual or the repair book i have. and I have been pulled over once for it - and dont want to pay the expensive shop prices for something that should be very very simple.
Thanks for all help.
J

What year car?

What year car?
its a 1995... i have also learned, from looking at the bulbs, it in fact does have two (dont know what they are called) but little wires that run across that light up..one fatter - brighter.

so there is a problem between the lights being turned on and the top, thin running light lighting up, if you know about that i would be super happy