I believe everyone is referring to the Immigration form. As The donkeycentrehalf points out the P&O guidance pdf suggests using the website or the Covid times BIMsafe app.
Before setting off on your Caribbean holiday, all guests are required to complete the Barbados Immigration and Customs form. This is available through scanning the QR code above. Otherwise this can be accessed through the website (https:// travelform.gov.bb/home) or BIMsafe app (https://bimsafe.gov.bb). This form will be available to complete 72 hours prior to travel and it is strongly advised that this is completed no later than 24 hours prior to travel. Once you have completed the form, you will receive confirmation via email which will contain a QR code. (Make sure this hasn't gone to your junk folder as you will need to show this at check in before your flight to Barbados)