Navigating in worlds is pretty difficult from the get-go so here's a basic guide on how to use the UI and menus provided.
Tutorial By Pilgrimm
There is a panel in the top right that will help you with the more social aspects, like communication, avatars, and saved locations. In the bottom right, there is a box with buttons that can help you navigate the surface-level worlds. We'll start with the social panel.
In the options, you have a place to edit your friends list, mute list, change your camera angle, sign in/out, and so on You can look up and down by pressing Page Up and Page Down on your keyboard.
The Home key resets it to default.
I have an extra option to turn on Shaper because I've already enabled it. (Go into your worlds file > click the text document/ini file that says "worlds" > paste DISABLESHAPER=0 under gamma to enable shaper)
In the edit friends panel, you have the ability to add friends by typing their username instead of clicking on their physical avatar and adding to friends. This can be useful for when you want to add someone while they are not online. You can also delete friends.
Just type the name when this window appears. Usernames are not case sensitive.
Returning to the panel in the top right, you'll see the 4th option is Worldsmarks. Clicking it will bring up this list:
Wherever you are standing in a world, clicking Add new WorldsMark will save that exact position and add it to your list so you can return to it later.
You can name your WorldsMark for the sake of list organization. I suggest you make the name specific so you know exactly where you're going when choosing from the list. The URL is how you can share or adjust the WorldsMark.
If you click the change location option, it will open a window that shows only the URL of your current position.
To go to a WorldsMark someone has linked you, remove the current URL and paste the given URL in the box. It should send you to the provided world.
If using a 3D avatar, you will be able to use actions, which can be found in the top right corner as the second to last option.
Clicking any action will activate an animation. Only 3D avatars will perform the animation. In the bottom right is Sleep, which is the sign that someone is AFK. If you idle for 10 minutes or type "brb" in chat, your avatar will automatically fall asleep.
The last option on the panel in the top right is VIP. Clicking it will give you options to change your avatar and visible users.
Choose avatar shows you a list of all the default worlds avatars you can use, including both 3D and holographic. In the Saved Avatars option, you'll be able to save and delete your avatar.
Any avatar you are wearing at the time you save will be added to a list under. You can name avatars the same way you can name your WorldsMarks.
The Customize Avatar option will open up a menu that will let you change the look of your avatar. I suggest using a mirror and changing your avatar view to first person (found in the options). There are two mirrors downstairs in GroundZero (the place where you spawn) by the auditorium that can be used. There are also several in the avatar gallery.
In this menu you can change the head, head size, face, and colors of the avatar. You can also do this in the Metamorphics room in the avatar gallery if you need a visual reference.
The last option in the VIP Menu is # (number of) Visible Users.
This window allows you to change the maximum amount of avatars you see at once. The effect does not mean per room, but the space around you. Users who are further away from you will not be visible until you approach them. The amount of avatars on screen can affect performance.
In the bottom right corner is a mini map. You can click on the locations to navigate easier.
The worlds provided here are simply the most popular surface worlds, as clearly not every one would fit. Some custom worlds have it and some don't. Occasionally an image will be put there instead of a map.
Here's the mini map for Jimbly's world.
Is worlds not running? No textures downloading? No worlds accessable?
Run the game as admin. If that doesn't work, reinstalling will fix it. Make sure you have Java 6 installed before playing.
Some AMD users may have issues downloading/using worlds.