If you're switching from another rank tracking tool that supports CVS export, you can import the rank history for your website into your Rank Tracker project in a few steps.
For each date, create a CSV file that features the same list of keywords in a separate column. For each search engine you'd like to include, add the Rank and the Ranking URL columns.
Below is a sample file with 2 search engines ready for import:
To import the data, open/create a project for the exact same domain.
Make sure that all the search engines used in your import files are added to your project (or add the missing ones under Preferences > Preferred Search Engines).
Go to File > Import > Keywords... and follow the wizard to import the file you've prepared:
Repeat with the files for other dates if needed, and make sure to save the project with all the new historical data imported.