I can help you with that c:
If you're on a normal computer, you can make spoilers by clicking the third icon to the left on the BBCode panel ( ) You'll see this window:
Just click the "Please select" field and select Spoiler. Then, you'll have a spoiler (after choosing what goes in it)
If you're on mobile, you can just type [&spoiler&]*Insert whatever you like here*[&/spoiler&] (but without the &s!)
As for spoilers, on a computer, you just select some of the text in a post by whoever you want to mention, hold your mouse over it, and click "@Mention."
. Say I wanted to mention you. I would select at least one letter of a post of yours, then hold my mouse cursor over the part I selected. A window would come up with two options, "Quote," which lets you quote just what you have selected, and "@Mention." I would click "@Mention," and then you would be mentioned.
However, this does not work on mobile devices. To make a mention, you write [&member=Member'sNameHere&], again, without the &s.