You do not need an external meter to find the satellites. In fact, the meter will not be as good as the internal meter in the receiver. You should take the receiver and a small TV out to the dish for an easier install. The receiver must be configured to work with the connected LNBF in order for the meter to work or a satellite to be found and channels viewed. You most likely will need a remote control to enter and adjust the menu settings.
For example, if you want to try out the receiver and view one of the promotion channels on a Dish Network using the 18" dish and circular LNBF, set the receiver to the 119 satellite and select LNBF type Standard with LO frequency of 11250 (assuming that the LNBF is not labelled DishPro). Set the Transponder Frequency to 12457, Polarity Vertical (to receive right polarity circular), and Symbol Rate 20000.
Use a dish aiming calculator such as
GeoSatFinder - Satellite Finder Calculator - Satellite AV to assist with adjusting the approximate dish elevation and azimuth (compass reading). SLOWLY pan the dish 10 or 15 degrees either side of the compass heading while observing the Signal Quality reading. IF the Signal Quality reading doesn't show the satellite signal, increase or decrease the elevation by 1 degree and SLOWLY sweep the same area again. Repeat until the satellite is located and the Signal Quality is peaked.
Once the Satellite Signal Quality is peaked, perform a Transponder Scan or Blind Scan the satellite. As Tron indicates, you will only receive a few free channels, but this will assure you that the receiver is working until you can order of locate a proper dish. You will need a 90cm/36" dish with a linear type LNBF to receive FTA channels.