Green fingers...not so much

I love having flowers and plants at home, but there's a reason as to why I've always made sure it wasn't me who took care of them, I don not have green fingers what so ever. Now however there is no one else and I don't have any other choice than to try my best. Unfortunately the no green fingers statement seems to stand strong...I bought this flower on friday, today it's monday and this is what it looks like...what? how? I just don't understand.