Step 1: Use "Gene" command to generate lny, lnx2, lnx3 and lnx6 : For example lny

Step 2: Choose "Estimate Equation" from "Quick" option, the Equation Specification dialogue box
            will appear

Step 3: In the dialogue box, type lny, c, lnx2, lnx3 and lnx6, then click OK button.

Result:

By computing, the modified R² = 0.81

The income elasticity and the own price elasticity have the correct signs and are statistically significant at the 99% level. The cross-price elasticity coefficient is not statistically different from zero; the p value is 0.644.