You use the div css codes.
Here is the example one. Fill in the blanks

<div style="width: #px; height: #px; background-color:----; 
overflow: auto; overflow-x: hidden; overflow-y: scroll; ">

all the stuff you want in the box right here!
</div>

Put in a number for width.
Put in a number for height.
Replace background color with a colour OR leave it how it is for an invisible box.
Overflow x: hidden means you don't have a scroll on the bottom. Anything that goes wider than the box just disappears

Overflow Y: scroll means that it scrolls vertically.

No problem.