BirchPress Scheduler free plugin out of the box is really ugly, missing styling. So here's something to get you going.

BirchPress Stylesheet

/****************** BirchPress Scheduler *****************/

#birs_appointment_form .birs_field_content, #birs_appointment_form .birs_form_field select {
max-width: 100% !important;
}


#birs_appointment_location {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

#birs_appointment_service {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

#birs_appointment_staff {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

.ui-datepicker .ui-datepicker-header {
position: relative;
padding-top: 4px !important;
background: rgba(192, 192, 192, 0.31);
color: black;
height: 30px;
}

#birs_appointment_form .ui-datepicker table {
font-size: 1.2em !important;
}

#birs_appointment_form .birs_form_field textarea {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
}

#birs_client_name_first {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

#birs_client_name_last {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

#birs_client_email {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

#birs_client_phone {
  background: rgba(192, 192, 192, 0.31);
  border: 1px solid rgba(182, 182, 182, 0.71);
  border-radius: 0 !important;
  height: 28px !important;
}

button, html input[type="button"], input[type="reset"], input[type="submit"] {
  border: 1px solid #67A100;
  background: #67A100 !important;
  border-radius: 0 !important;
  padding: 6px 10px !important;
  color: #fff !important;
  margin-left: 6px;
}

button:hover, html input[type="button"]:hover, input[type="reset"]:hover, input[type="submit"]:hover {
background: #85d100 !important; 
}