How to install User Scripts

Does anyone know how to install User Scripts in Blender ?

I am trying to import animated models from Mixamo. They have a Blender guide here Mixamo: Quality 3D character animation in minutes

They also provided a Blender plugin to import the type of DAE files Mixamo produces. Problem is I dont know how to install Blender user scripts.

Can anyone please help me out ? Do I simply paste the Python scripts into BLender addon directory or something else ?

File / User Preferences / Addons panel
Use the Install Addon button and select the addon script.
Then enable the addon with its tickbox.
Use the Save Settings button if you want this addon to be enabled everytime you start blender
See https://www.blender.org/manual/extensions/python/add_ons.html

Alternatively split your 3d view and set one half to be a text window. Load the script into the text field and use the Run Script button.