Using the enumitem package, \usepackage{enumitem}
:

If you need this behavior locally you can directly insert in the options to enumerate
the specifications of your labels. If you need it global, then set in the preamble the same as Bernard's answer, \setlist[enumerate,1]{label=\bfseries\arabic*}
. You can remove or leave the dot as required or add spaces where needed.
\documentclass{article}
\usepackage{enumerate}
\begin{document}
\begin{enumerate}[{\bfseries 1.}]
\item some item 1
\item some item 2
\item some item 3
\item some item 4
\end{enumerate}
\end{document}
This approach is particularly easy if you don't want to remember names, e.g.,
[\bfseries 1.] % for Arabic numbers
[\bfseries I.] % for Capital Roman
[\bfseries A.] % for Capital alphanumeric, ...etc.