You can try looking at zolowear zolowear.com/Wearing.aspx website they have instructions and videos...think I found it useful...still have it bookmarked anyway... I was never very successful at breastfeeding my LO in mine ... did use it as a cover sometimes when sitting. Even so I did find it extremely useful -in fact I class one as a baby essential (I still use mine now at 18 mo -mainly as reins)
The easiest thing to do first is to put it very loosely around you with the rings on your collar bone, same side as boob to be used, latch baby on, and hold them with the opposite arm to boob in use. Gently tighten the sling around them, and then put the free arm under baby, remove arm from sling, and replace under. Continue to tighten, until you feel it take the weight.
If you search for nursing ring sling on YouTube theres some great videos
I used my ring sling all the time until DS was 14 months, and happily fed him in it walking around.