linksys wrt54gs

my unit is 12 yrs old and i think been working fine. I live in the remote so have never set up the security on it, and was going to do that. I had to reset password, so all is ok...so far. I go to look at the wireless sercurity settings and see there is only...
pre-shared key
psk radius
radius
wep
I went online to get a youtube tutorial, and they have same router with several other different things to choose from. I thought I needed a firmware update.
My router is a version " 1 ", so it's pretty old. I did upgrade it, per the website...uh but still only have the above settings to choose from.
So, which am I to choose? I don't find much info on any of these, or which to use. Perhaps the radius one, because there really is not anyone around us, over 200 feet? Pleaes advise. Just trying to be a bit more secure. Thx

Use Google search for:
pre-shared key
psk radius
radius
wep

and that my help decision process.

i did and 3 of those didn't really show. i just went with shared key and made my own P/W. much easier.