Im looking for @disneysurvivor. thanks!!
Search for the user using the magnifying glass at the top… then click the name to go to their profile and there is an option to send a message.
Alternately you can click on your picture at the top and select messages and start a new one and simply type the name into the to box.
Since you tagged them, just click on their name. It brings you to their profile and there is a link to private message.