Firstly, most modern hearing aids automatically adjust the volume based on the environment around you (i.e., quiet vs. loud environments).
If you would like to adjust the volume manually, the following can be done for behind-the-ear and in-the-ear hearing aids:
Behind-the-ear hearing aids: The volume can easily be adjusted by pushing a button on the back of the hearing aid. The exact adjustment instructions will vary depending on your hearing aid model, so read your device’s instructions for more details.
In-the-ear hearing aids: Remove the hearing aid from inside your ear and find the volume button to adjust the volume.
Additionally, some hearing aids are accompanied by an app where you can adjust your hearing aid volume from your phone app.