Once you know which release you wish to add to your Wantlist, within the search results you can swipe right on that release to see the following options: Want - Own. If you tap "Want", the release will be added to your Wantlist. After tapping "Want", the option to remove the item from your Wantlist will display as well.
You can also add an item to your Wantlist from the release page! After accessing a release page, you will see two badges at the bottom of the page: Add to Wantlist - Add to Collection
When you tap Add to Wantlist, the item will be added to your Wantlist. If you wish to remove it, simply tap the same button which now displays as "Remove From Wantlist".
You can also view your Wantlist by tapping on the Wantlist icon located at the bottom-left of the screen or from the top-right menu and accessing Wantlist.
When viewing the Wantlist, you can search for a specific item using the Search Bar and typing the title, name or label of the release. Sort the list by Artist, Title, Year, Added, Label, Format and Catalog #, or filter by Format.
If you would like to remove an item from your Wantlist, simply swipe all the way to the left on the specific release and tap Delete.