Step 2 asks which committee you want and which portfolio in it. Both are required.
Choosing a committee
The list shows every committee the secretariat has marked active, in the order they chose. Each entry shows the committee name and its agenda. Committees that run double delegation are marked as such, which matters for the next step.
Choosing a portfolio
Type the portfolio you want, such as a country name. It is a free text field rather than a dropdown, deliberately: it accepts portfolios that are not on the published matrix, so you can ask for something unusual.
Tip
Open the matrix in another tab first. It shows which portfolios in each committee are still open. Naming one that is already taken is not an error, but it does mean the secretariat will have to give you something else.
This is a preference, not a booking
Nothing is reserved when you submit. Typing "France" does not hold France. The secretariat reads everyone's preferences and then allots portfolios by hand, so what you get depends on availability and on how many people asked for the same seat.
Giving a second preference on the next step makes it considerably more likely you get something you actually wanted.
Spelling
Write portfolios the way the matrix writes them. "USA", "United States" and "United States of America" are the same seat to you but three different strings to the system, and matching them up is manual work for the secretariat.
Next: partner or second choice.