After you created your items database you need apply list to form fields.
By click menu of Dashboard --> BSK GF Blacklist --> Apply to Form --> Add New, you will be navigated to apply list to form field screen.
All fields of the chosen form will be listed out and let you apply your list to a specific field.
The Comparison column can let you select the logic of how users input match your item.
Same means the length and characters all same with any item in the list you chosen.
Contains means the users input contain with any item in the list you chosen.
Case-insensitive Same:itEM1 MATCHS item1
Case-insensitive Contains:itEm1 and item2 MATCHS item1
Case-sensitive Same:item1 MATCHS item1
Case-sensitive Contains:item1 is our capital MATCHS item1
For Email list the comparison is default to the users input same as any email( item ) in the chosen list.Purchase BSK GravityForms Blacklist