Obtaining an avatar...

When asked 'Select avatar or choose avatar later' I chose the later option, and consequently am invisible!
How do I obtain an avatar after passing this initial stage??? I wish i had just selected one off the list now! Am i missing something really obvious?

No problem Victoria.
You have an inventory yes?
open it, select library.
select clothes or objects I can't be sure.
In there you should see folders labelled things like goth male, nightclub female, male shape, female shape ...
drag folder icon to the centre of the screen where the cursor should turn into a rectangle and let go.
You should .. 'materialise'

I had a similar problem when I first started. Not sure if this is your problem too but you want to click on the preferences button at the login screen, then go to the graphics detail tab and uncheck all the shader options and set avatar rendering to normal. You might also want to press the M and esc button a few times to make sure you are not in mouselook.

I wouldn't recommend turning off all those shaders and rendering options unless you've got a low end video card that can't handle SL the way it's meant to look. The world is a very different and much prettier place with all that stuff turned on.

In any case, follow Bree's second suggestion, and make sure you're not in mouselook before you do anything else. "Mouselook" is SL's term for first person view, if you didn't know that already. When in mouselook mode, you're looking directly through your avatar's eyes, so of course you can't see yourself. To exit mouselook, press escape a few times, or if you have a mouse with a scroll wheel, scoll downward to zoom out. When in mouselook, you're zommed all the way in.

If you're not in mouselook, and your avatar has indeed turned invisible, it's no big deal. When that happens, it's usually due to some temporary glitch. It's possible the new avatar you selected just failed to load for some reason. In most cases, you can fix that by changing av's, as Bilbo suggested, or by relogging.

I'd suggest you clear your cache (the button for that is on the network tab in preferences), and then relog.

What you described shouldn't happen. I imagine you were having slow loading times due to the network being overloaded, which has become the norm these days. The other posters have all offered good suggestions. I'm sorry you had such a crummy first-time experience.