Installing a VIM plugin in Ubuntu is not that complicated as it used to be. All one has to do is put the plugin in a proper folder. However, do not confuse yourself VIM with VI. By default Ubuntu comes installed with VI and not VIM. Even if you put the VIM plugin in the proper place, it will not reflect in this editor.
First install VIM.
For Ubuntu it is just sudo apt install vim. This is the critical step. Next is NERDTree a popular plugin and a must have for any VIM user. The path to put a plugin for NERDTree is similar as
~/.vim/pack/vendor/start/nerdtree
So any plugin will live inside ~/.vim folder. There might be a chance this folder does not exists!
Create ~/.vim folder
Inside that create pack/vendor/start folder. Then create a folder with the name of the plugin. If the plugin is available in GitHub, clone the repository in this folder. That is all to it.
Here is the link to NERDTree
Configuring VIM further can be started with .vimrc file present at ~/. There might be a chance, this file does not exists! Start by creating a file at ~/ with name .vimrc.
Here is my list of useful comands for VIM.
Happy Coding.