To get the most out of Stacker you need to tell Stacker which data type is stored in which column in your Worksheets. For example: is a column a date? or a piece of text? or a number?
You can do this from the Worksheet settings page. (Same place you set the ID field).
From Setup Home (you can access this via the Settings cog in the top right of every screen), select the Settings option for the first Worksheet.
Then press Expand next to Configure Fields.
Press on the cog next to each field.
Select from the available data types in the box that pops up.
Repeat this for every column on the Worksheet, and then for every Worksheet in your app.
If you have any relationships between your Worksheets then you can tell Stacker which column relates to which Worksheet.
To setup relationships follow the instructions above to Specify your data types and then select Link to another record as the type.
Then pick which Worksheet the column relates to.
Repeat this process for all relationships that you have in your Sheet.