Hey Sam, it's pretty simple. You need to create the popup as you want it to be. For example, if you want to have a darker backgrounnd and the popup on the middle too add deph, create a div with absolute positioning, 100vw and 100vh. Then add the popup centered inside that div. You simply need to add aa show hide formula on the background div, you can use a variable for example. Then simply set the variable "popup_visibility" initial value to false, whenever you want to show the popup create an event setting it to true.
There is a video on toddle yt channel about conditional visibility explaining all of this
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