From within your project's database, click 'Auto-build or import' to import data:
You can upload a .csv file (comma-separated values file, AKA a spreadsheet). You can create a .csv file from any popular spreadsheet software, including Excel or Google Sheets.
Your .csv file must have at least 1 column of data that is suitable for the key column of your Afterpattern database (meaning, that column is comprised entirely of unique values). If you don't, you will get this error:
^ This error is telling you that the column in your .csv file that you're attempting to use for the key column in your database has duplicate values (note, if two cells of data are empty those two cells are duplicates).
There are two ways to fix this: