student in Hong Kong wants to go to mainland

Rafael, you must have a HK ID, right? If so, you can apply from HK. As your wife doesn't have this document, it's hard to say whether she can apply from there as well. If she can, you can submit the applications to the Office of Commissioner of PRC Foreign Affairs Ministry. The required documents include your passports, passport copies, application forms, recent photos, an invitation letter from your friends, and the original and copy of your HK ID and your wife's tourist entry permit.