CMS has two ways to enroll to be a Part B provider: paper based and web based through PECOS. Details can be found here.
Additional questions can be directed to your Medicare administrative contractor or MAC. You can determine who your contractor is and located contact information here. There is no fee to be enrolled for outpatient services, but there is a fee to enroll as a durable medical equipment provider, which is required in order to bill Medicare for orthoses (see below).
CMS requires a separate enrollment if you plan to provide orthoses or supplies for Medicare beneficiaries. This enrollment requires an enrollment fee along with additional information. Learn more