Want to visit HK to see my friend, so how about the visa issue?

You can ask your friend to provide you an invitation letter first.
May I ask whether your friend a HK permanent resident or a non-permanent resident?

You need to prepare your valid passport, an application form with a recent taken photo, your bank statement, your flight tickets to HK, your friend's invitation letter. If your friend is a local resident, he/she needs to provide the copy of the HK ID card. If not, the copy of the passport is required. After you prepare all the documents, you can mail these documents to HK Immigration Department to apply directly.