Welcome to FT Hussyd!

I've alerted a mod for you to move this post to the BA forum where you'll likely get more informative answers as well to update the title of the thread to something more descriptive.

However, the question is broad and depends on your type of ticket and how you want to upgrade.

Some questions to consider that will affect the answer (the more information you provide, the more people can help):

• Are you looking to upgrade from World Traveller to World Traveller Plus, from WT+ to Club World, or from WT all the way to CW?
• Did you pay with money for your flight or is it a reward booking?
• If you paid, what fare class?
• Are you looking to upgrade with money, with Avios, or with oneworld partner miles?

Good luck!