Ignore the red filter, they're not very useful.

The timer does in fact switch on the enlarger, that's what it's for. While I don't have that model, timers usually have two purposes:
- to switch the enlarger on for focusing (usually a dedicated button), until switched off, and
- to switch the enlarger on for a finite time. You set the time somehow (buttons/dials/whatever), press Go and the enlarger should come on for the specified time.

Yes, enlargers are very dim. Paper is pretty sensitive stuff. You will need to focus your image with the lights OFF, preferably with the safelight off too. You will want a focus-aid/grain-magnifier to see proper focus (edit: Ok you have that).

Ignore the Trinar lens if you can't clean it (cleanliness in the lens is important or you will get a flat image). Go spend $20-$40 on a 50/2.8 Rodagon or Componon-S or EL-Nikkor.

The filters change the image contrast when using variable contrast (VC) paper. You will need a set, but they're pretty cheap and easy to find. Plenty appear on APUG, and probably there are several sets in your local camera shop for like $5 each. I'd send you a spare set that I have except that postage from AU will cost you 3x more than what you'd pay for a set locally.

The stop and fixer will be perfectly fine. No you can't develop paper in Ilfosol; go get a 1L bottle of Ilford Multigrade.

To focus the enlarger, you put the easel under it and then put the focus finder on top of the easel. Approximately focus the image onto the easel with the lens wide open, then make fine adjustments while looking into the focus finder. You should see the grain snap into focus - that's where you want it. Then stop the lens down about 2 stops (probably f/8 will be best on your lens) and start making test strips and then a print.