Epic Link is not a field that takes options, the list is generated by having Epics exist in your system. There's no where to actually add options because that's not how it works.
The best you could do is add a select list with all your own Epic links defined as options, and then have an automation that updates the actual Epic link.
Of course, that's a little clumsy, and it won't stop people changing Epic link to an Epic not on your list. You'll also need to think about what to do if someone does that and selects an Epic you haven't listed - you don't want to destroy their information by re-applying a new one if someone edits your field (simplest solution: only automate this on the creation of the issue, and don't put your field on any screen other than "create")
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.