readme edit (installation instructions)

README.md

@@ -9,12 +9,16 @@ You are free to use this code, but no warranty whatsoever is given.
 ## Installation
 
 
-To install the package, run the command below. It is assumed that you have git and pip installed on your system.
+To install/upgrade the package, run the command below. It is assumed that you have git and pip installed on your system.
 
 ```bash
 pip install git+https://gitlab01.esss.lu.se/ess-bp/ess-python-tools.git -U --user
 ```
 
+If you have installed using Anaconda, we recommend to not use the argument `--user`.
+
+The argument `-U` implies you should upgrade if you have already installed this package but a newer exist. `--user` implies that this should be installed for the current user only (usually in the folder ~/.local/lib/).
+
 ## Usage
 
 Here we will briefly explain how to use the library.