From your question, I assume you do not have the owner's manual. The link at the bottom of this page will take you to the Henry website, and you can download the manual.
You can download a manual here - http://www.henryrepeating.com/freestuff.cfm
Best to ask a gunsmith for assistance.
The rifle does not need to be disassembled to clean it. However, if you want to, the owner's manual has instructions for PARTIAL disassembly. The link below will take you to the owner's manual for that rifle. Would suggest you print and keep a copy.
Ask a gunsmith for help
Do not atttempt this. Find a gunsmith.
WHICH Henry? The antique Henry rifle made in the 1860's or the current Henry Repeating Arms Co rifle?
http://www.lymanproducts.com/lymanproducts/LymanUsersGuide.pdf
Best left to a gunsmith.
Recommend a gunsmith be allowed to do it.
Recommend you let a gunsmith do it.
Ask a good gunsmith for help