If you click on Setting (top right of the page)
On the left you will see a number of items, scroll down until you get to General settings
In general settings, scroll down until the options on the right show the title Miscellaneous Options.
Under the "Message Editor Interface" select the type of editing you want. Some browsers can't handle the Enhanced interface, but that is the one I use and I get the option to change fonts and add smilees.
Standard Editor might do that as well -- you will have to play around with it.