Sync device option, this feature will allow you to build a database using Dropbox which you can use to synchronize devices with that database for you to have access anywhere. To set this option you would first need to do it from the computer you will use to create the master database, so if you are going to build the database from your PC you should start the process from the PC. To set this option you may open Express Invoice and go to Options > Sync Device > Sync this device with other devices running Express Invoice > select Dropbox and click on Connect. Enter your Dropbox credentials and wait until the synchronization completes. Once you have the PC synchronized you can follow the same procedure from the other devices you wish to connect and each device should be assigned a letter, so the first device (PC) should be Letter A, second device letter B and so on.