Open following links to help identify product and download typical manual:http://www.rheem.com/Products/tank_water_heaters/gas_water_heatershttp://www.rheem.com/product.aspx?id=CC643E03-4C15-4775-B139-E504A95651F7
Usually, the instructions for lighting water heater are on side of tank, and located at gas control.
If you add a comment and describe gas control in detail, and add if model has piezo igniter, I might be able to provide specific instructions for that gas valve.
Also include if wires on bottom of gas control go to a switch located on combustion door.http://waterheatertimer.org/images/IMG_9146-gas-control-thermo.jpg
Make sure basement has plenty of fresh air to support combustion.
Clean combustion parts and air intake.
Check that thermocouple sits inside pilot flame.
If no gas comes out of gas control when trying to light water heater, then check that gas valve handle is parallel with gas line. Gas pressure might be low. Gas might have air in line.
If pilot lights but will not stay lit, then thermocouple might be bad.http://waterheatertimer.org/pdf/How-to-replace-thermocouple.pdf
Many factors can contribute to water heater not lighting or staying lit.
Get started, and then add a comment with steps taken so far, and what you observe for more help. I will be here most of the evening. Aug 1, 2011.
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