Copy as much as you like from the sample emacs config. You will need at least the VHDL-Tool flycheck checker definition.
Then, start the vhdl-tool server and then Emacs:
$ vhdl-tool server & $ emacs
You can also access VHDL-Tool's built in language server from within Emacs with the lsp-mode plugin. This exposes all of the features of VHDL-Tool from within Emacs. This method is currently not well tested.
An Emacs configuration file to get you started can be found here.