Question

Once you've chosen a topic what should you do next

Answer 1

The one that you should do next is brainstorm to get out initial ideas

After choosing a topic for your research, you ideally had already understood the answers you intend to seek from your research.
From this point, you need to sit together with your research team to find out the methods that you can use in order to find out that answers. Usually, this will come up in the form of small and simple ideas at first, but it will bring your team closer to the goals