One of the options when defining a slice is to choose which columns to include. Below, you can see a "Slice Columns" section: this is where you can do so.
To determine which columns you want to see, select inside the text box that contains the column names (i.e. Name, State, etc). You may choose just one column to display in your slice, such as Name here:
Or you may choose to have multiple columns as part of your slice, as shown here:
You can also reorder the columns in the slice.
Once you have decided which columns you want in your slice, remember to save your changes. The system may automatically add back columns that are required for the slice to operate correctly (usually, this occurs with key columns that have been unintentionally excluded from the slice).
To see what is displayed in your slice, select "View Data". This example slice would open a new tab showing this table of data based on the columns selected: