It seems like there is no official website for the International Chemistry Olympiad! All the information (problems from previous olympiads, solutions, results, etc) are available for each year on a different website specific for that year.
[PowerPoints] General Laboratory Skillsby Keshav Dhandhania
The following PowerPoint files cover general laboratory skills that students participating in IChO should be familiar with. Specific equipment details will vary, but the operating principles will be the same.