The two URLs you posted are the same. Did you mean to ask about something else?
In any case, I can't offer guidance on setting up Jira itself, but based on the reference to "request token" in the first screenshot, it looks like it's meant for OAuth 1. The current version of the Dropbox API doesn't support OAuth 1, however, only OAuth 2. (The /2/auth/token/from_oauth1 endpoint is only for converting old OAuth 1 access tokens if you still have them; it isn't for processing the OAuth 1 authorization flow.)