I think they are LBMS but I did not realise that they were stickers?
They are more a kind of stickers than anything else.
1) To punch out the boss hole in the middle, ude a leather multi-punch (if the shield is GB plastic, the 4th punch fits exactly)
2) cut out the design as neatly as possible with a sharp pair of scissors (some peeps use the curved nail scissors type)
3) Now peel off the clear film on the FRONT (yes- you actually see the back of the sticker, so a mirror image of the finished shield) of the transfer/sticker. I use the point of an x-acto to get an edge opened. The sticky part is under the film, so careful!
4) Apply the sticker to the shield, and try to avoid air bubbles
5) To ensure a snug fit, you can use a bit of blu-tac (or the likes) covered with a small piece of cling film and press it against the shield (remember to stabilize it with the other hand, so it doesn't break off)
6) Dip a finger in clean water and dab it on the paper on the front of the sticker so it gets soaked (a small drop or two suffices).
7) Wait a bit, until the paper come loose (10-30 secs). Remove the paper
8 ) Paint boss and any rims
9) apply a good layer of gloss varnish to seal the sticker (this is important - I've heard ppl complain that if not sealed, the sticker may dry out and shrink)
10) Aply matt varnish
The shields on my viking warband are all LBMS