How do I fix the counter weights in double sash windows? and how to take these windows off?

[KatM]

How do I fix the counter weights in double sash windows? 

I recall seeing several years ago somewhere a video frim bunnings on YouTube I think showing how to do this, however, I am unable to locate this. Does anyone have a video on how to do this to these specific type of windows and also any advice on how to fix them as well as what materials are needed and can I get these materials from bunnings? 

In addition, how do I take these windows off so I can paint the other side (you'll see in one of the photos, paint missed).  Thanking in advance.