On the FORM screen - What is the default forms DisplayMode set to?
In design mode, click on the form and go to the DisplayMode (Top Left-hand corner)
I suspect that it is DisplayMode=DisplayMode.NEW
So its giving you a blank form which it is expecting you to fill in.
You will have to tell the app to switch modes between NEW, EDIT and VIEW - depending on your situation.
As a newbie, I would suggest that you duplicate the Screen.
Call the screen something like 'Screen_Edit' and the Form named to 'Form_Edit' (or whatever you like)
Then on Form_Edit set DisplayMode=DisplayMode.View (OR DisplayMode.EDIT if you prefer)
Now click on the 'FORM_Edit' form, and change the Source property to the name of the table where your data is coming from.
This tells the form where to get the data from.
In your case, I think that the table name is PowerBIIntegrations.Data -
You can find the correct name if you click on the data sources icon on the left)
Then (Still on the FORM_EDIT form), change the ITEM property to
First(Filter(PowerBIIntegrations.Data, ID_FieldName = Selected.Gallery1.ID_FieldName))
Replace ID_fieldname with the name of the field that uniquely identifies the record that you want to show.
This property says : Show me the first record that exists in the source table (PowerBIIntegrations.Data) where the ID_FieldName (in the source table) matches the ID_FieldName that has been selected in the gallery.
Now select the Screen that has the Gallery in it and
Click on the Gallery.
Find the OnSelect property (Top left-hand corner)
and set its value to : Navigate(Screen_Edit)
So now, when you run the app, every time that you click on an item in the gallery, it will take you to the Screen_EDIT screen for you to edit the existing record.
Your next challenge will be to add a SAVE button to this screen and write the code to Patch the data.
