I just bought my first Strat yesterday. MIM . It had a floating trem and would not stay in tune at all. I really don't use it much, so I loosend the strings, then tightend the trem screws so the bridge stays tight to the body. Is this the proper way, or can I add 2 springs to do the same thing. Any advice would help. New to stratocasters, but already LUV mine...now to learn to play better...lol

Either or mate.
You can do either and achieve the same result. Or if you want to be double sure, you can do both.
Personally the one guitar that I don't use the trem on, I blocked. So if I want to go back to using the trem on it. All I have to do is remove the block and re-tune.

Don't dismiss your trem. You can set the trem up to give good stability, without having to shell out on over hyped products. But thats a maybe for after you get used to it.
Congratulations on the new guitar.

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No no and no

Your's is a common Stratocaster question. Highly recommend you do a search on this site and on Google, etc., and you'll find a wealth of information.