How to install this Plugin with vim plug

[LeducH]

I want to use this plug in. I use vimplug as a plugin manager

what is the command I have to add in my plugin block

call plug#begin('~/.vim/plugged')

" Make sure you use single quotes

Plug '????????????????????????????????'
call plug#end()

[mawkler]

Both

Plug 'rhysd/vim-grammarous'

and

Plug 'https://github.com/rhysd/vim-grammarous/'

should do the trick.

[likesan]

Hm.. I wonder why there isn't a guide for installation in README.md

[SpyrosMourelatos]

Hm.. I wonder why there isn't a guide for installation in README.md

Because it is pretty standard, and it is already documented on whichever package manager one prefer.
It could be bothersome for one plugin creator to have to write down 20 different ways to install the plugin(which are essentially the same thing).
For example, vim plug documents that on it's examples
with lines as such

 " Shorthand notation; fetches https://github.com/junegunn/vim-easy-align
Plug 'junegunn/vim-easy-align'

" Any valid git URL is allowed
Plug 'https://github.com/junegunn/vim-github-dashboard.git'