Add basic functionality

README.md

@@ -22,6 +22,8 @@ modes/layouts:
   for using git
 - [helix](https://helix-editor.com): A postmodern text editor. Replaces
   vim/neovim.
+- [xclip](https://github.com/astrand/xclip): A command line interface for the
+  system clipboard in X11/wayland
 
 For some plugins, extra tools are required. These are optional, and only needed,
 when the plugins are installed:
@@ -35,5 +37,11 @@ Before any plugins can be loaded, it is neccesary to install the plugin-manager
 itself. This has to be done manually, and can easily be done by using git:
 
 ```bash
-git clone https://github.com/tmux-plugins/tpm ~/.config/tmux/plugins/tpm
+git submodule add https://github.com/tmux-plugins/tpm ~/.config/tmux/plugins/tpm
 ```
+
+Then, the `tmux.conf` file can be used. Make sure, when editing the file, that
+the structure of the file is kept. It is mandatory, that the tpm command must
+remain at the end of the file at all times for TPM to work properly!
+
+After adding a plugin, press **Ctrl+\<prefix> I** to install the plugins.