First, at least one player has to initiate bidding. You do this by entering the MaBiWeb match ID. The match ID can be found to the left of the match listing on your Game Manager page. It can also be found near the top of the match page where it says, "Nations Game ID=".
That will load the match into BidBot and take you to the results page for the auction. You should now see a button at the bottom of the results page that says, "Bid". If you don't see that button, then you probably need to link your MaBiWeb account to your BidBot account.
At this point, you can share the link to the results page with the other players or they can also initiate, which will just take them to the results page. The match will only be loaded once. An example results link is https://bidbot.tabony.net/nations/mabiweb/81435/
Press the button to bid. You'll see a form where you can enter your bid for each of the nations available in the match. You are bidding points. Once everyone has bid, each player will be assigned one of the nations in the match using the auction algorithm. Each player will have to subtract the points they bid for the nation they were assigned from their score once the match is complete.
Bids can be in half-point increments. Examples of what you can enter are, "0", "0.0", "0.5", "1", and so on.
You are allowed to bid the same value for more than one nation! If you do, then when you press "Review Bid", you will see another form where you must rank your preferences for those nations. These preferences will be used in the case that you win the bid for more than one of these nations.
You will have a chance to review your bid before locking it in. Once you have confirmed your bid, you will not be able to modify it. Choose wisely!
After confirming your bid, you will be taken back to the results page, where it will say that you have placed a bid.
Once all players in the match have placed their bids, the bids and the resulting assignment of nations will be revealed!
Good luck and have fun!