Followed by this message:

And finally see this:

You are trading and placing units for the red team. You can click on units with the mouse and then hit "Remove unit" to take it off the field of play. You'll then be credited with build points to spend.

So, we remove a few units and got some points to spend. You can see that we have 9/15 points on the field already, so we need to spend 6 more.

The pulldown menu above the "Points 9/15" lets you choose which unt to place. Place it (if you can afford it) on any available square. You can only have one unit per square.

If you want to move a unit, you can remove it and place it again; there is no penalty for replacing units.

We swap in some new units:

And we've spent all the points, so you hit "Quit" in the lower right. You'll get a chance to send a message to your enemies. This will appear AFTER your move has been processed (or, in this case, after your units have been placed):

Then, you'll send off the file to the Servinator as with any move. You should expect a reply from the Servinator saying that it got your mail.