Play a concert F note on the F side of the horn. Use the tuner to see if the pitch is flat or sharp. If the pitch is flat, push in on the small F tuning slide. Identify this slide by finding the small slide that is not directly connected to a valve. If the pitch is sharp, pull out on the slide until you achieve the correct pitch.
Depress the thumb valve and compare the F concert pitch from the F side of the horn to the B-flat side. Adjust the main tuning slide on the B-flat side until both sides play the same pitch, pushing in if the pitch is flat and pulling out if it is sharp. The main tuning slide on the B-flat side of the horn is the largest slide on the horn. It is also not directly attached to a valve. The timbre between the two sides of the horn will be different, but the pitch should be the same. Use the tuner if you need help determining if the pitch is in tune. If you only have an F tuning slide, skip this step.
Play a B-flat, below the staff, using the F side of the horn and the first valve. Depress the thumb valve to switch to the B-flat side and tune the 1st valve B-flat pitch. Make small adjustments in tuning by adjusting the first valve slide inwards if it is flat, and pull out if it is sharp. You can identify the first valve slide because it is attached to the first valve.
Tune the second valve by playing the fourth-line D on the F side of the horn. Adjust the second valve slide that is attached to the second valve. Depress the thumb valve to play the pitch B on the B-flat side and ensure it is in tune. Push in on the second valve slide if the pitch is flat, pull out if the pitch is sharp.
Push the third valve tuning slide all the way in. This slide will be attached directly to the third valve. Play the second-line A on the F side of the horn, using the first and second valve. Alternate to the third valve to play the same A. Return to the first and second valve. Pull out the third valve tuning slide until the pitches match.