Wrap your content with .avatar class and wrap your text in .avatar-content to create a avatar.You have to use inline attributes to set height width of image in default avatar.

use class .avatar-{sm|lg|xl} to modify size of your avatar.

use class bg-{color-name} to change background color of your avatar

You can add notification label to avatar by using .badge with .badge-up

use class .avatar-status-{online | offline | away | busy} after .avatar-content to create avatar with status