I am unable to connect to the package repository server using MiKTeX due to a proxy error. How would I go about installing a package from a local repository? I am trying to install the package beamer. Where do I actually find the file to download?
You need to get the packages from the miktex folder on ctan:
Put whatever you want to install e.g.
in some empty folder (outside miktex).
Beside this you need the three database files
http://mirrors.ctan.org/systems/win32/miktex/tm/packages/miktex-zzdb1-2.9.tar.lzma http://mirrors.ctan.org/systems/win32/miktex/tm/packages/miktex-zzdb2-2.9.tar.lzma http://mirrors.ctan.org/systems/win32/miktex/tm/packages/miktex-zzdb3-2.9.tar.lzma
Put them also in the folder. Then you can use the folder as local repository.
From https://ctan.org/tex-archive/systems/win32/miktex/tm/packages, download to a directory on your h.d.
beamer.tar.lzma and the 5 following files:
You have to declare the local repository from MiKTeX console, Settings, like this: