@Happy Scuba Susan were you able to see your baggage allowances in the Manage Booking section of their website and find where you can add an additional bag? I don't work for Fiji Airways but am happy to help a fellow diver.
If I'm not mistaken, baggage allowances can differ based on your itinerary, which is why you would want to check on the specifics for your booking. Policies do change, but for what it's worth, mine from LAX > NAN > KDV and back was
carry-on bag: 15lbs 45in. max (height + width + depth)
checked bag: 66lbs 62in. max
personal item max weight 8.8lbs with no stated dimension restrictions but has to be something like a laptop bag, purse,
handbag, pocketbook, small camera or small laptop backpack.
I guess different people have different experiences, but I've flown Air Pacific/Fiji Airways on seven trips now and always had a very enjoyable flights with warm and friendly customer service. On our last trip inclement weather delayed the NAN > KDV flight, but even then the staff I dealt with were very kind and helpful.