Well hello, Basic End User!
Since you are a Basic End User, the most important thing for you to understand is that you shouldn't install the default OpenWrt load. Why? Well, it involves all of this nasty "command line interface" stuff that will give you hives, or at least make you very uncomfortable.
Here's the good news. You can get a lovely web interface by relying on the fine folks at x-wrt. They basically repackage the default OpenWrt with all of the crunchy web browser goodness that you expect now-adays. Read all about it or go get it.
There are those that say "X-Wrt is too large!" Well, you judge for yourself. Would you rather have 1.8MB of data uploaded to your router, and have to type stuff like
ntpclient -c 1 -d -s -h 0.pool.ntp.org
Or, would you rather use buttons and clickable fields to set the date and time, and occupy 1.9MB? If you answered 1.8MB, this is the wrong guide for you!
If you're still here, you now need to figure out WHICH firmware you want (since it's very hard to upload firmware that you haven't chosen yet.) So:
- Figure out the firmware that you need (search the Wiki for the model number of your router)
- Download the firmware from x-wrt rather than directly from the openwrt.org site (see above)
- Upload the firmware to the router.
BEWARE: Some of the web interfaces on some existing routers (such as Buffalo) will NOT allow you to upload new firmware, because they do checks to see if the firmware is from THEM.
In these cases, to upload this new firmware, you may wish to invite a geeky friend over who understands arcane mumbo-jumbo like default IP addressing schemes and can do magical things like tftp.
However, if you CAN use the web interface on your existing router (such as Cisco's Linksys -- here is a good example), you will likely be in good shape to upload the firmware.
Good luck!