These Practice pages can be utilized in several ways.

The recommended method is for two partners to be in vocal contact, each looking at the page in a different computer - perhaps one with a laptop. Using this method one partner would start by clicking on NORTH, the other on SOUTH.

Somewhat less satisfactorily, the partners can use a single computer, and alternate looking at the display, again one as NORTH, the other as SOUTH.

As a last resort, one person can click back and forth between screens.

Start by clicking one of the buttons; when the bidding is complete click the BIDDING button to check the "recommended" bidding.
 You are the Dealer.
 Bid this hand with your partner.
 The opponents do not bid.
 Your partner, NORTH, is the Dealer.
 Bid this hand together.
 The opponents do not bid.

Yes, this has nothing to do with Gerber or Blackwood, but everything to do with smart bidding.

SOUTH has a 16 points and NORTH has 15, 16 or 17. SOUTH wants to be in 6NT if NORTH has 17, but merely a Notrump game if she has 15 or 16.

The way to find out is to bid 4NT - not Blackwood but merely an invitation to bid 6NT. In this case, NORTH has but 15 points and declines the invitation. If her Q were changed to the A she would bid 6NT and collect her twelve easy tricks.
♠ K 7 5
Q 9 6
A 9 8 3
♣ A Q 7

♠ A Q 6
K 7 3
K 6
♣ K 10 6 5 3