All Sunday and Wednesday Divine Services feature the Sacrament of Holy Communion. (Matins, a prayer office, does not.) There is no need to request permission simply to attend services. Regarding Holy Communion, however, visitors from other LCMS churches are asked to notify the pastor or duty elder before partaking, and other visitors are asked to make an appointment with the pastor first.
For those unfamiliar with the practice of closed communion, a short video can be found here.