Multiple Linear Regression


Im trying to forecast an economic predictor and our professor hasn't been very clear as to what to do for this project. I know I am supposed to use multiple linear regression
y = b0+b1x1+b2x2+...

to my understanding, I have found b through holding my variables constant and regressing through time. Do I do the same with my economic predictor and use that as x? and Does x1 have to be different than x2?

Thank you