By enlarged prostate, I assume you mean that you're suffering from difficulty starting or stopping your urine flow, dribbling, frequent urination, incomplete emptying, urgency, poor sleep due to frequent urination, etc. Prostate pain and painful urination are not included in this list as they are more consistent w/prostatitis and urinary tract infections.
If you're only aware of your enlarged prostate because your physician commented as such, and especially if you're not suffering from any of the above symptoms, we typically don't recommend any treatment for an asymptomatically enlarged prostate.
On the other hand, if you're suffering clinically due to prostate enlargement, there are several things you can do. First, avoid diuretics such as caffeine & alcohol which just make you urinate more. Second, avoid the typical older cold & allergy medications available over-the-counter w/o prescription here in the States. Examples include diphenhydramine and phenylephrine. Pseudoephedrine use to be available but has been removed from the market. These drugs can make it more difficult to empty your bladder and thus aggravate an enlarged prostate.
Some folks swear by nutritional supplements such as saw palmetto, pygeum & nettles. Unfortunately, the evidence to date doesn't support their use. However, this may be due to the variable quality of these over-the-counter supplements that are manufactured without any third-party oversight.
If you need more help than can be achieved by the above, your family physician may offer you medications to either relax the prostate capsule or shrink the prostate or perhaps do both. Alpha blockers come in two general groups, those that lower blood pressure (and thus are useful in someone w/high blood pressure) and those that don't, both of which relax the prostate capsule in a short period of time.
5 alpha reductase inhibitors (5ARIs) take up to 6 months to shrink the prostate (and in doing so, drop your PSA by 50%). One of these 5ARIs, finasteride, sold as Propecia, has also been used to slow hair loss. More recently, there has been some concern that 5ARIs are associated w/high grade (worse) prostate cancers although it also appears that they lower one's overall risk for any prostate cancer.
While a PSA of 3 is normal with 4 as the upper limit, we like to see lower numbers in younger patients. Thus, it's more important to compare your current value to previous ones. If this is your first, it may be just due to your enlarged prostate. With that said, it still bears close monitoring.
And let's not forget Family History. The more male family members w/prostate disease, the more concerned we are about your prostate. So make sure your physician has all the information necessary to help you make the best informed decision.