This is a great question that, unfortunately, cannot be answered in just a couple hundred words. There are important issues that focus on educating one's self prior to embarking on such a course of action, particularly the downsides of using steroids – the side effects, the proliferation of fake gear, getting off of them, getting blood work done, etc. And, the fact that buying, selling and transporting them is (in America) still a felony, not to mention banned by all sports federations. All very important salient issues that require a lot of space to do justice.
Anabolic steroids can cause the development of acne. However, the extent to which it is experienced can be due to a number of varying factors, with the particular steroids and exact dosages used being primary. The skin´s sebaceous glands have a particularly high affinity to Dihydrotestosterone, which is an androgen the body naturally produces from testosterone via the enzyme 5-alpha Reductase. Increased sebaceous gland activity promotes oily skin which can combine with bacteria and dead skin (normal wear and tear) eventually causing pores to become clogged more quickly than the body can cleanse them. This of course, is preventable by using only particular steroids, cleansing the skin regularly, and perhaps using a topical anti-androgen.