You can only import notes to an existing deck at the moment, so you must create a deck first.
You should start with an empty deck to avoid mixing new notes and old notes together.
Step 2: Go to "Import notes" option and choose your CSV file
CSV file must conform to a predefined template to be imported successfully. Get the latest template file on your import page.
CSV file content must be strictly in the right format, otherwise the import process will fail.
Step 3: Wait a little bit for new notes to appear in your deck
If your CSV file is small, you might not have to wait at all.