Search is the orange-bordered white-inset at the top-center of the map. If it is not displayed, tap the map to display.
The default category is named. This is notably the name of guide pages on HAZ but is also lots of other results.
Categories on MapDEX include: named, trails, routes, areas, places
Search begins finding results on two letters per word.
Recommended: Three letters per word PLUS the two-letter state abbreviation.
ie: camelback echo az
The above example may be found easier. Understanding of the recommended procedure is key.
tonto forest perimeter az 
willow fire az 
charlebois spring az 
1) forest and wilderness are typical used perimeters
2) zoom to area > Options > find perimeter is a better alternative. You will go crazy looking for Chediski Fire because it is really Rodeo Chediski Fire and it was entered on HAZ as a single word Rodeo-Chediski without spaces around the hyphen. Search starts at the beginning of each word. Not all fire perimeters are in the database. If a specific fire perimeter seems missing, you may request via the help button in the lower-right corner of the map. Requests are not guaranteed but maybe.
3) Charlebois is one of the top misspelled words on HAZ. The bigger issue is that the example returns a lot of results. Results sort by distance to the red crosshair. Getting in the habit of zooming to the general area before using search is best.