When you want to compare the means of three or more samples, a one-way ANOVA test is the appropriate test to use.
This video shows you how to open an Excel file in SPSS, and to set up the data for running an ANOVA test. It compares the means of three samples and show step-by-step how to run the test. The video finishes with using the Tukey test to determine where the differences are between the samples.