How can I treat prostatitis that's caused by chlamydia?

No such thing. Chlamydia doesn't cause prostatitis. It causes nongonococcal urethritis (NGU), which can be misdiagnosed as prostatitis. Genital chlamydial infections are best treated with a single dose of azithromycin, 1 gram; or with doxycycline 100 mg twice daily for a week.
Antibiotics. The treatment of choice for chlamydia infection is antibiotics. Other infections and std's are usually present as well and should be evaluated and treated for as well. If there is pain and discomfort, one can take tylenol (acetaminophen) or motrin.

Related Questions

If prostatitis is caused by chlamydia or an STD and u test neg for the STD in a urine sample but got prostatitis from oral sex. Is it contagious?

Yes. chlamydia is contagious no matter how you contracted it until you are treated effectively. Read more...
Prostatitis vs STD. Prostatitis is not an STD and not sexually acquired. Chlamydia doesn't cause prostatitis. However, prostatitis has overlapping symptoms with some STDs, especially nongonococcal urethritis (NGU); it can be hard to tell them apart. NGU can be acquired oral to penis but chlamydia only rarely. Prostatitis is not contagious for sex partners. The risk to partners from non-chlamydial NGU is uncertain. Read more...