You can use a tuner by just playing each string in front of it and then just turn the fasteners until the tuner shows that the sound matches its appropriate sound.

Another way is by ear, press down on the fifth fret and the preceding string in which you are trying to tune. For example, if you are tuning the high E string, press down the B string, 5th fret.

Strumming the B stringwhile pressing down on the 5th fret should make the sound of open E string.

Match the sounds of both strings and this will tune the high E string.