Where can I select an independent-samples t-test in SPSS?

Yes, learning by doing is the most effective way.

Thank you. I will try by myself. 

You may click Analyze > Compare Means -> Independent Sample Test. The Independent-Samples T-Test window opens, where you will specify the variables to be used in the analysis. All the variables in your dataset appear in the list on the left side. Move variables to the right by selecting them in the list and clicking the blue arrow buttons. You can move a variable(s) to either of two areas: Grouping Variable or Test Variable(s). Test Variable(s) is(are) the continuous variable(s) whose means will be compared between the two groups. You may run multiple t-tests simultaneously by selecting more than one test variable. Grouping Variable is the categorical variable indicating the groups of the independent variable that will be compared in the t-test. The grouping variable must have at least two categories (groups); it may have more than two categories, but a t-test can only compare two groups, so you will need to specify which two groups to compare. You can also use a continuous variable by specifying a cut point to create two groups (i.e., values at or above and below the cut point). When finished, click OK to run the Independent Samples T-Test.