Newbie question about Surface Pro 1 pen

I bought a refurbished Surface Pro1, 4 GB Ram 128 GB internal storage, running Win 10 Pro for $240 Canadian.
It comes with Microsoft backlit type-keyboard cover which is a great value. I prefer type-keyboard over touch-keyboard.
However it does not come with the pen.
I purchased a pen online. It works great.

I have a newbie question :
Please see the screenshot + the question below.
What are those "accessories" meant for ?
I suspect those are replacements for the "tip" ? But how do I use them.
And what is that metal ring for ?

I know nothing about those but you would probably get much more help if you had posted this in the main forums. Hardware maybe? This IS the Chill Out room you know. Just sayin