Mechanics' lien claims are filed with the prothonotary of the county where the property is located. Properly filing and enforcing a mechanics' lien claim is a very technical and difficult process. It is advisable to get an attorney to assist you with such an effort.
That said, I'm not sure you'd be entitled to a lien in your situation. Here is an excerpt of the section of the statute that creates the right to a mechanics' lien:
"Every improvement and the estate or title of the owner in the property shall be subject to a lien, to be perfected as herein provided, for the payment of all debts due by the owner to the contractor or by the contractor to any of his subcontractors for labor or materials furnished in the erection or construction, or the alteration or repair of the improvement, provided that the amount of the claim, other than amounts determined by apportionment under section 306(b) of this act, shall exceed five hundred dollars ($500)."
Are your cleaning services accurately characterized as "erection", "construction", "alteration", or "repair"? Are they for over $500?