Popup Maker plugin allows to create a nice popups and the integration with Uni CPO makes it possible to open such popups by clicking on tooltip "?" icon. An example of such integration can be seen here Fields Notes Notebook (click on "?" tooltip).
Create a new popup and configure it. Also create a trigger, similar to this one:
Note the CSS class used here. It is .uni-popup-class. Actually, it can be any unique class, but it is important to choose any.
Enable using tootlips for an option and choose "Popup Maker" type and add the CSS class you used for the trigger in the previous step: