Click on this link to use a site that will allow you to play your instrument and see how the pitch needs to be tuned-must have a microphone.
For a personal device you can also download an app that is a "Chromatic Tuner" (there are several free options).
How to tune/use a chromatic tuner videos:
Intro to tuning: https://youtu.be/Ezp3Sd4tXZU
Chromatic tuner (how to): https://youtu.be/cG63Y7010Zs
Tuning with the pegs: https://youtu.be/5vgzi4d2V8k