My best guess with the teensy amount of information you've provided so far is that the display you're using isn't compatible with the controller the bike came with, which is completley normal. In general, displays only work with the controllers they come with as kits, for "full" functionality (and sometimes not even then). Sometimes they work with certain functionality with other controllers of the same brand, but are unlikely to work at all with any other controllers.
My best recommendation based on that same teensy amount of information is to replace the controller already on the bike with a new one that comes with it's own display, that is already able to do all the things you want it to do and display.
Additionally, since you don't typically reply to those trying to help you, for whatever reason, all of your posts have been merged into a single thread here in the Ebike Troubleshooting section, so that you are more likely to see those replies you do get (which are less likely to happen without you also helping us help you), so that whatever information we might be able to provide is more likely to be seen by you and perhaps help you solve your problems.
(and you'll have spare magnets if needed)
