How do I get to my filters and labels?

Desktop:

Filters and labels can be accessed in your Settings. Tap on your OnMail avatar → Settings. From the sidebar you can view your filters and labels, add additional ones, and delete ones you no longer need.

Mobile:

You cannot create filters on mobile, but you can add and remove existing labels to emails.  From the inbox select all the emails you want to apply a label to → More → Add to Label.  You will see a list of existing labels to use.