Kindly follow these steps to apply a tag to past orders:- 

1. Select Past Order from the top navigation menu of the app
2. Start the process of tagging to past orders by selecting the rule from the  search bar and range of orders as per your requirement
3. After selecting the rule click on ‘Start Processing‘ and trust the process. 
   note:- (Usually, this process takes up to 30 minutes. However, it can vary accordingly to the number of orders.)