Unfortunately, it is not possible to search for and find another user by name using a full-text search.
However, you can search under "Discover" for example by age, gender, last online and more. Simply tap on the small magnifying glass in the "Discover" tab.
Were you registered for a meeting that took place with the user you are looking for? Then you can find him or her under the "Chats" tab under "Acquaintances".