Use to play flute and is planning to relearn what is the best way?

Start with the basics. If those come quickly then you'll find it easier to move onto the harder stuff. I would suggest a lesson book, Rubank ones are good. Start at elementary then move up from there. Don't jump right into the harder sets, start and make sure you have the basics down really well first. PRACTICE EVERYDAY! It doesn't matter how good you used to be, it's a matter of how much you remember. If you stopped in 5th grade after only 2 years of playing the rest of the players are going to be TONS more experienced. At least 30 mins of practice everyday and you should be fine. Good luck and all the best!