That can all be done through the phpMyAdmin app, usually accessed through your hosting account or cPanel. Changing collation is fairly strait forward. Changing actual character encoding is more involved since it impacts how the data is stored. It’s essential to make a backup before changing actual character encoding. A proper query needs to be run to alter character encoding. There is no UI element to do so.
You can switch collations through the appropriate UI elements in the app. Be aware that there are several independent collation settings in a DB. The overall DB has one, every table has one, and every textual column in a table has one. You’ll want to change them all. There may be a query that does all of this in one fell swoop, but I don’t know what it’d be.
