To upload your references into Covidence, navigate to your review in Covidence, and click Import References.
In the dropdown menu below Import in to, select 
the folder where you would like the citations to
go (Screen).
Browse to the RIS, NBIB, XML, or CRS text file you would like to upload and attach it, then click Import.
It may take some time, but you should see your citations appear in your systematic review on Covidence within the next few minutes.
If you want to reverse an import, you can do so as long as you have not screened any articles from that import.
In the import menu, select Import History.
Each file you import will be listed. If you have not screened articles from this import, you will see an Undo this import button. Clicking the button will remove the entire import from the review. If you have already screened articles, you will see a Check Duplicates button instead. Imports cannot be undone at this stage.