What do you mean you can't figure it out?
Open IMVU.
Launch a 3D window.
Move the mouse to a corner of the window, click and hold while you move the mouse pointer to stretch the window to a larger size.
Dress you avatar how you want.
Move the camera to frame your avatar how you want.
Pose your avatar how you like by either selecting the mood you want doing an action or expression.
When your avatar is just like you like it press Ctrl+Print Screen.
Open an image editing program.
Paste it and save it. Programs normally have an option in one of there edit menus. They are likely to also use the shortcut Ctrl+V.
If you don't use photobucket or anything upload your saved file to your IMVU snapshot gallery.
Grab the link to it and post it.
If that doesn't help.....
*grasps frying pan.