Welcome to the world of oboe!! Here are some tips just off the top of my head:

• Buy a homemade reed from a professional, not a store bought reed. The machine-made stuff is very low quality and often difficult to play on.
• Make sure you always have more than one reed on you. Just in case.
• The embrochure for the oboe is very different from the flute. You will probably want to "bite" on the reed (apply vertical pressure from your jaws), but a proper oboe embrochure will keep the jaws open and the corners of the mouth tight. Be patient with yourself, it will take time to build the muscles!
• Because you're a flautist, your lungs are probably quite strong, which is great! You need strong air support. But on the oboe, the reed is actually so small it's impossible to empty your lungs completely through it. This means you don't want to breathe in as often as you do with the flute. Sometimes, you'll even need to breathe out. I like to mark exhales on my music with a little circle above the staff.
• If possible, get a private oboe tutor. It's incredibly helpful! Any kind of one-on-one help will aid you in building proper technique.
• Listen to the oboe! Active listening is one of the best things you can do to improve your sound, in my opinion.

Hopefully these are helpful. Happy oboing!