Adding a control variable and testing for significance

"Perform a controlled comparison, with a test of statistical significance."

That's what I'm trying to do. My independent variable is "religious importance," a four-category ordinal variable. My dependent variable is "moralism," a 17-value variable that I'm treating as interval. I would like to control for age, an interval variable.

My question is how can I test for statistical significance with the control variable added to the mix? I already did a two-sample t-test for my IV and DV, but I'm not sure where to go from there.

Thanks for any assistance.