Shinjuku interchange Yamanote to Chobu

Am wanting to go from Shinjuku to Inoshikira Park. Shinjuku looks very complicated. Apparently there is an "interchange station" between Yamanote and Chobu lines. What does this mean and any pointers please about navigating this. Many thanks.

Am wanting to go from Shinjuku to Inoshikira Park.

Then, you should take the JR Chuo Line from Shinjuku Station to Kichijoji Station, from where the park can be reached in a five minute walk. No transfer of trains is required.

I gather from your question you are arriving by Yamanote line at Shinjuku and then need to change to the Chuo line: don't worry, signage in all the major Tokyo stations is excellent, and relatively easy to follow: also, we found at Shinjuku there were plenty of station staff in the main concourses: if you are worried just ask one of them: they certainly understand sufficient English to happily help you. Have the Tokyo transport map with you, and have the places marked so you now which way the train should be going