How do you add two independent master's degrees to your name?
Unless you are in a place that regulates academic titles, you can do pretty much as you please. But you could qualify each with the specific field or university if you feel the need to list both.

FirstName LastName, M.Sc.(Basket Weaving), M.Sc.(Basket Burning)

Distinguishing by university, rather than field will probably confuse people, thinking you have two masters in the same field. Qualifying with both is probably too unwieldy.