Inside the parentheses, place the page number(s) you're referring to and the author's last name, unless you mentioned the name in your running acknowledgment. If more than one work by an author was used, include a shortened title of the work you're citing. For example, if you had used more than one book by Erich Fromm, your note would read as follows:

According to Erich Fromm, it is through the act of giving that we experience our fullest strength and potency (Loving 19).

If you had not mentioned Fromm's name in the running acknowledgment, the entry would look like this:

One psychologist believes that through the act of giving we experience our fullest strength and potency (Fromm, Loving 19).

As you can see, this isn't difficult. Do remember, though, that the parenthetical note shouldn't repeat information from your running acknowledgment.