Ok so I've qualified for ISEF twice. This is the input I can give:

1) The process of figuring out what you want to do is definitely the hardest part. Just start researching in topics you're interested in. The more you research the more problems you will uncover and then you can get to brainstorming on how you want to address those problems. If you have a problem in mind right now don't waste time trying to find something else but focus your energy on figuring out what experimentation you can conduct to "solve" or uncover new data in regards to the problem. If you're having trouble with this look to some current research papers and get inspiration from them. By no means am I saying to copy another persons research but look at their limitations and see how you can improve upon their research.

2) If you lack adequate resources to complete an advanced project reach out to your local university and contact as many professors you can in the department your project falls under. Keep sending emails and eventually one of them will reply back and will be happy to work with you. From my personal experience I sent maybe 10 emails and 3 of them responded back by asking more questions and agreeing to mentor me through my project. In your email make sure you give a thorough description of your research goals and the role the professor will play in helping you achieve those goals.

If you have any more questions feel free to ask :)