Hi Prema,
When you get a fake moustache like that there might be quite a lot of visible “lace” (the backing material) around the edges. The extra lace makes the piece more durable (for surviving washing etc) but if you’re closeup in a larp, rather than on a stage, you probably want to trim away as much excess as you can with a small pair of scissors.
Use a mirror to position the piece on your face and work out where you are going to glue it on.
Use a prosthetic adhesive (I sell that, by the by).
Apply a very thin layer to the back of the piece. Really thin, it should be nearly invisible. Let it get transparent and tacky.
Apply a similarly thin coat in the center of your upper lip/chin.
Fold the hair piece in half with glued side out and hair side in, place the piece onto the centerline of your face.
Once the center is on, you can lift one side of the piece and place it near your face to see where to put the glue. Apply that, again, as thinly as you can. Once it is tacky, press the edges into place. If it is long or very styled, using a comb rather than your fingers can help prevent messing up the style of the beard.
Note: The glue works like Ados, once you stick it down it will be stuck, so be careful. Also that looks like a pretty light piece, you might get away with just glueing the edges, which would make it a whole lot easier to remove!
If you get a bit of glue shine around the edges, start by just tapping your fingers on it. If that doesn’t work, put a tiny bit of face powder or talc on your fingers and tap it again.
I hope this helps. Have fun!