Well, আপনি go to the part below were it says share page, x বন্ধু online and two আরো symbols. If there are বন্ধু online, আপনি click on their name(not exactly the name but when আপনি put your মাউস there, it will get darker, then click there). When আপনি click there, another little window will appear and you'll have a little box where আপনি can write. There আপনি write and can chat!
I've copied the page I'm on now, and the part that's in a darker blue(were it says drgroz), is where I've put the মাউস ;)
