i would reccomend putting them in your mask first. then attach the other magnets on the outside of the mask. put a dot of hot glue or some other kind of marking agent. put your Bio down where you want it. then the dots will mark where the Bio should fit. take off bio and glue magnets to bio.
You actually only need magnets either on your helmet, or your mask, but not both.
I attached magnets to the inside of my helmet with JB Weld and affixed a large metal washer to the inside of the top of my mask. The magnet (3 rare earth magnets glued together) was positioned in a corresponding spot on my helmet. I had to dig out some of the foam so that I could get the washer as close to the surface as possible. It works great, and I didn't have to figure out how to get magnets to stay attached to latex.
Ahhh I see but i only have magnets like 50 of em soo i am going to use thoses hahha but i have nothing inside the mask to glue it on unless i glue it to the top of the mask but shouldn't there be somthing behind the magnets to keep it in place? You see what I am saying? Unless I have some kind of foam to fill in the mask like some other masks.
I have mine set up the other way around...magnets in the helmet, and a big metal washer in the latex/mask. The JB weld holds like nothing you've seen before, so I don't worry much about the magnets pulling off from inside my helmet.
And with the rather large washer being in the mask, this kept me from having to use a metric ton of magnets (rare earth or other) to make contact between the two. If you use magnets on both items, then you have to be pretty close as to where they are attached so that they can grab hold of each other.
And that, is a really big pain in the keister.
If you want to glue the magnets to the inside of your latex mask, I have no idea what you could use to bond those two different materials together. Just about any adhesive will fail due to the flexibility of the latex.
That's a whole different matter, and not something I have experience with. I'd suggest that if you don't know how to do it yourself, that you send it to someone who has experience foaming. If this is your one and only mask, it would be best not to let it be your guinea pig.