Proposals are accepted in August/September, reviewed in October/November, and approved to move forward in November/December.
I'm expecting an official call for proposals some time in the next few weeks, which will have more details about how to submit your proposals. Meanwhile, be thinking about
- what problems you need solved,
- which domain in IHE might be able to hep you solve it,
- how the situation might look if the problem no longer existed.