I really dislike the use of the word "adopt" in reference to an animal of any kind. People adopt children, buy animals or sponsor the care of one elsewhere. If you sponsor a child in another country needing care, do you say you adopted him or her? Many words seem hijacked by the animal rights agenda and "adopt" is only one of them. The diluting of the meaning has went even further- I saw an ad to adopt a trailer (mobile home) the other day and almost fell off my chair! In interest of what is most often searched the title uses the word "adopt".
Learning how to adopt a monkey as a pet is not something everyone would choose to do personally. For those committed to doing so, here is some information. For those deciding to adopt a monkey by financially supporting one in a zoo or other facility there are also ideas given.
How to Adopt a Monkey as a Pet