Okay so, so far you're doing really well!
Up above your text box are a bunch of little white squares with lines, symbols, and jigged up letters. Click one.
I clicked the very first one on the top, on the left. The big, bolded 'B'.
If you click that, letters in your text box will pop up. Thay will look like this;;
Well, where you see the two ' ][ ' inbetween the b's, type "Hello!". It should look like this when you type it.
Now hit post. Ths result should be;;
Now try it with the other boxes. And try them all if you want.