It's easy if you have Luma3DS:
Turn your 3DS off.
Hold the start button while booting up your 3DS and select "GodMode9".
Next select "SYSNAND CTRNAND", then select "dbs", then select "ticket.db".
Select "Ticket.db options..." then select "Build encTitleKeys.bin".
Voila! You now have the file, which is located on the SD card in "\gm9\out\encTitleKeys.bin".
Next, copy it to "3ds\data\freeShop\keys" and rename it to "download.bin".
Reboot your device.
Open freeShop again, all your titles should now be there!