I have a Yamaha RBX170 I think its called. Its a pretty basic starter bass but the action is too high. I have gotten used to it but I would be able to play much better if the action was adjusted lower. I don't want to take it to a shop because I'm sure I can do it with your aid. So what doo hicky do I adjust to make the action lower? Do I just adjust the bridge some or is it more complicated than that?
Rhythm Harmony Melody
Check if the neck is straight. Lower the bridge if you can. You can probably forget about a new nut if you don't want to take it to the shop, unless you have a spare femur lying around.
How may The National D help you waste your time?
I get charged around 50 aus or so... depends on where you are and where you go. Is the neck straight? You could try some truss rod shenanigans if it's the neck and if you feel up to it.
How may The National D help you waste your time?
The manual for your bass probably shows you how to adjust the action... my bass didn't come with one, so I had to Google it. I'd assume you could find one for Yamaha basses online as well.

But You could probably get away with just adjusting the bridge.
2006 Warwick
If you don't know what you're doing, take it to your local music shop. Believe me, you don't want to mess around with your action if you don't know what you're doing.
http://www.tunemybass.com/bass_setup/adjusting_neck_relief.html has a good description on how to set your truss rod and the linked article in the page has a description on how to adjust your string height or action. Read these, if they don't make sense, your next step should be to heading to your local shop and luthier.

Where I live a good set up costs anywhere from 35 USD to about 50 USD. The price usually will include a set pf new strings as well.