There are many things to know about dessert wines but they are beyond the scope of these lessons.
The important wine facts to know at this point are that the glasses for dessert wines are usually smaller because the amounts served are smaller. The amounts served are smaller because the wines are quite intense with sugar and sometimes much higher in alcohol.
If your establishment does not have dessert wine glasses, you should use a white wine glass or tall Champagne glass for still dessert wines, or a Champagne glass for sparkling dessert wines.