Use the D-Pad to highlight the list of settings, and mic button to select them. There are three settings for you to change: the type of measurement unit, the unit you want to convert from, and then the unit you want to convert to.

Click on each of the settings and use the D-pad to scroll through the list of options. Then key in the number of the original unit into a text box below the three settings. The converted amount will immediately be displayed below the text box.