So basically, when it's my turn, I open the save, work out what I think I might do, close the save again and then post my thoughts for discussion?
Hi Misotu, and welcome to this prestigious

team (This is going to be our SGOTM. I can feel it in my bones)
I guess the way it works out in practice is something like this (assuming you were following me):
AgedOne: finishes his turnset, uploads save and posts turnset notes.
Various Geezers (including Misotu): download the save and look at the current position. They all post comments about what's going on, how AgedOne got us into this position, suggest plans etc.
Misotu: posts stating officially that you've 'got it', and when you intend to play.
Misotu: Having taken into account any wishes of the various Geezers who posted, posts a brief plan for the turnset. Probably gives the team a bit of time for any final comments.
Misotu: Plays the turnset, eradicates Alexander, builds a wonder or two.
Misotu: Finishes the turnset, uploads the save to the server. Posts turnset notes.
And round we go again...
It has been known for the person playing the turnset to ask for advice without even saving and coming out of the game . . . though I must confess the last time I tried that I found no other Geezers on line
I've never done a screen shot & don't know how to do it (although I'm sure it's pretty simple with a bit of guidance

.)
You can take a screenshot just by pressing the Print Screen key. BTS understands that and places a (full screen) jpeg into the My Games\Beyond The Sword\ScreenShots folder. It names them something inscrutable like Civ4ScreenShot0005, so you have to decide which one is which.
Then there's a couple of ways of including the jpeg with your post. The one I normally use is as an attachment (the paperclip icon above the post you're writing). There's also Insert Image, but be warned that it will include the image full-size in your post. Not always what you wanted!