Accelerators are institutions that “accelerate” the growth of new ventures. The prerequisite to enter an (usually time-limited) acceleration program is a working prototype and initial traction on the market. By providing specific services, resources and contacts and accelerator enables the new venture to grow its business (i.e. increase its users/customer base, generate more profits) and to professionalize its organization in order to lay the foundation for scaling of the business.
You're expected to build something and deliver it to a market. The place or office is secondary.