There is a global mikveh directory on our site that is a link to www.mikvah.org. If that does not suffice, we suggest calling the local Orthodox synagogue in your area, which should be able to help you.
There should be no need for a special request. Read through the articles on this site for proper preparation. You might want to call the mikveh lady in advance to let her know it is your first time so she can guide you through the steps.
You do not indicate whether you are currently married. In general, halacha encourages mikveh immersion only for married women. However, in some communities unmarried women do immerse for purposes of teshuvah (repentance) on erev Yom Kippur.