On Denote, I don't see any option to change/update the Dropbox password, so I assume it's probably done during initial setup after installation.
I promptly uninstalled and re-installed Denote. No prompt to sync with Dropbox. While most newer apps would have a three-dot settings/overflow icon on the action bar, none can be found anywhere in the UI. Given that Denote was last updated October 2013, I'm not surprised.
Some tablets and mobiles have a bottom navigation bar, which may be used to call up the settings menu, but my Samsung Galaxy S7 does not display this. After some research, the workaround is to enable Assistant menu under Accessibility --> Dexterity and interaction. A floating icon shows up where you can call up the settings menu. From this point on, I was able to get Denote to start talking to Dropbox. However, my notes are still not showing up.
Turns out Dropbox dropped support for its v1 API on Sept 2017 in favour of v2. 2Storks, the developer of Denote, didn't update the app to make use of v2, hence sync functionality is broken. I was thinking of switching to Textfile, but turns out that that one was also not updated.
All I want is a text editor that syncs (two-way) with Dropbox. After evaluating a few apps, it came down to Monospace and iA Writer.
Despite what Monospace says, I can't find the option to sync with Dropbox. Syncing with Google Drive is a pro/paid feature. That said, I quite like the hashtag feature for file organization.
From my limited time with iA Writer, it seems to fit the bill. Syncs properly with Dropbox. Even supports Markdown. Swipe left and right to change views.