Gas and Oil Home Heating Furnaces - how to charge system?

I have a tank of R-22 freon and the guages necessary to charge my home AC unit. I don't have instructions though. How do you do it? My unit has frozen up several times this year already. I am told that this is caused by an airflow problem, input or output, or being low on freon. The filter is changed regularly (usually not very dirty at all) and all vents are obstruction free. The unit has not been charged in several years and I know that I need to have it inspected but I will not be able to get a repairman out for a couple of days and this weekend we are having guests. The system cools, but not as well as it should. I would like your help in adding refrigerant. If you can't tell me the answer to this question because of a legal issue, maybe you can just answer these questions? What are the optimal pressure readings supposed to be? Are the pressure ranges printed on the unit some where? Do you invert the tank to dispense freon?

Thanks!

were brand new,just installed, and installed correctly.Run unit 15 minutes,back pressure(low side)should be above 60psi,head pressure(high side)should be about 220psi...Thats all from me.Maybe someone else will answer your other ?s...PDF