To install miniconda on your linux environment you have to download the package on conda.io website.

To avoid conflicts between your python versions already installed I highly recommend to create a new variable on your .bashrc file to differentiate between versions. For example, you can unpack your python 3.6 on any directory and add in the .bashrc variable:

[user@andromache directory]$ wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh
[user@andromache directory]$ chmod u+x Miniconda3-latest-Linux-x86_64.sh
[user@andromache directory]$ ./Miniconda3-latest-Linux-x86_64.sh

After this operations you will follow the instructions, and go to the installation directory. The default installation is in the home directory.

[user@andromache directory]$ pwd
[user@andromache directory]$ /home/user/miniconda3/bin
[user@andromache directory]$ vi ~/.basrh

Then add the next lines:

 alias   trython=/home/user/miniconda3/bin/python3.6
 alias   contrython=/home/user/miniconda3/bin/conda

After updating you variables with source comand, you have installed miniconda on your computer. Now to install Matplotlib you only have to excecute.

[user@andromache directory]$ contrython install matplotlib
[user@andromache directory]$ contrython install numpy
[user@andromache directory]$ contrython install pylab