What does HR have to do with psychology?, doing this diploma will not help you out as psychology has nothing to do with HR, it will also be difficult to get a visa as there is no relevance between what you studied and what course you want to do.
You need to see what the Universities want. For example, some universities like the University of Toronto want a combination of a 3 yrs bachelor along with a master’s degree. Some like Ryerson University say, if your degree has a certain amount of subjects, then they will consider your degree equivalent to a 4 years degree. Also, most of them ask for GRE as well which I hope you have written or will write.
Psychology is something that will be most useful if you study in a University. Doing this diploma isn't going to help you gain admission into any University. It is just going to be a waste of time & money.
There are two options, one see a college which accepts a 1 year masters and do a masters degree in psychology or a field relating to that either in your home country or Canada.
Second, you can look for a University that has a bridging program, though those are mostly for bachelors, but you could still look around, or you can contact the University admissions and see what would they accept. There may be a University that accepts your current degree as an equivilant.
Don't be in a rush, take your time and do. This is your future, ultimately though it is your choice.