Enclosing list in a box

With standard frame, you need only add leftmargin=* option to enumerate list:


%---------------- show page layout. don't use in a real document!

  \begin{enumerate}[label=Step \Roman*, leftmargin=*]
    \item   item 1
    \item   item 2
    \item   item 3
    \item   item 4
    \item   item 5
    \item   item 6

enter image description here

(red lines indicate page layout)

If you want to put frames etc round your list environment then I suggest using tcolorbox as this will give you much more control. For example, you can produce

enter image description here

using the code:


\newlist{steps}{enumerate}{1}% create new steps environment
\setlist[steps]{%              configure the steps environment
  label=Step \Roman*,
\tcolorboxenvironment{steps}{% wrap the steps environment in a tcolorbox


    \item item 1
    \item item 2
    \item item 3
    \item item 4
    \item item 5
    \item item 6


A few comments about the code:

  • The MWE example appears to be using the enumitem package so, as above, I recommending using \newlist to define a custom steps environment and then \setlist to configure this enivorment.
  • The \tcolorboxenvironment{steps}{...} command wraps the steps environment inside a very simple tcolorbox, which is highly customisable. I recommend reading the tcolorbox manual, after which you can configure this to your heart's content.