Welcome to the Bunnings Workshop community @MegzC. It's wonderful that you've joined us, and many thanks for your question about attaching a gate latch.
With some work, this style latch could be fitted to your gate. However, it is designed for a gate frame and post that are both square. You have a tubular gate frame, so that's one of the items you'll need to overcome. You could potentially screw the latch bolt into a tubular post, but I'm not sure how secure that will be. There is a Lokklatch round post version, but it suits a round post and round gate frame, which wouldn't be suitable once again. A helpful team member at your local store's Special Orders desk would be happy to enquire with the supplier to see if we could get a round post latch bolt as a spare part. That could then be used with the standard square post kit.
The second issue is going to be how tightly your gate is fitted up against the post. The main latch body, external access assembly and latch bolt are not just mounted on the surface of the gate and post. They have tabs that need to fit in between the gate and the post for secondary fixings. From your picture, there doesn't appear to be any room at all to accommodate this. You'd need at least a 10mm gap between the gate and post to fit this locking mechanism.
Let me mention @redracer01 to see if he can think of a more suitable locking mechanism or a way around these issues.