There are three sub-categories in the Basic Information Menu of UFC Undisputed; General, Height/Weight, and Skin/Physique.
General -- In this section you'll give your fighter a name and a few nick names the announcer will use to introduce you. You can select your home town (which will also determine your country), the city you fight out of, and your age.
Height/Weight -- Use the left analog stick to determine your height and weight, up/down changes your weight, left/right changes your height. The weights are predetermined for the weight classes, and unlike your height, affect your fighter's performance, as well as the division in which you compete, your maximum strength, speed, and cardio attributes. You'll see all of these attributes displayed in the screens upper right corner.
Skin/Physique -- You'll see three choices in the Skin/Physique sub-menu for you to choose from. Skin Tone allows you to choose your fighter's skin tone. Body Type determines your fighter's muscular composition; will you be long and lean or short and powerful? The third choice Face Type is a starting point for your fighter's facial features, which can be refined further in the Physical Appearance sub-menus.