Importing a SQL file in N99panel is pretty straight forward. Our import process easily handles large SQL files  ( > 500MB ) which on most other systems or via phpMyAdmin is problematic. But in N99panel it is real easy
Broadly it involves following steps. Here we assume that you have already create a system user and a MySQL DB
At your local system, compress the file into a zip file (if not already done so)
Upload the file to the system's user home dir via a SFTP client like FileZilla
Within N99panel console, go to 'Restore an Uploaded MySQL File' functionality and fill in the necessary details.
Once you submit the details, the restoration of the SQL file to the MySQL DB will begin in the background.
That it. Ideally it should work smoothly, but is some cases due to version differences of MySQL/MariaDB setup on N99panel and the source setups at where the dump file has been generated, the import process can fail.
Even when a background job is completed, under N99panel please go to 'Tasks', and check if any errors have been reported. Even after a deemed successful importation, please verify the table count on the restored DB. This should match with the table count in the imported SQL file.