It depends on the type of tuner you have. Remember that:

Db = C#
Ab = G#
Db = C#
Gb = F#
Bb = A#
Eb = D#

Your tuner might have a setting for "automatic tuning" and "manual tuning". With automatic tuning, you hit a note and the tuner automatically picks up what note you're closest to and then tells you how close you are to it. With manual tuning, you pick the note you want the tuner to lock on to. If you can set it to manual and then pick the notes above, it may make it easier for you.

What are the buttons on your tuner?