SPSS help

How do you find the variance of composites in SPSS, I can only make SPSS produce a covariance matrix but what does that help me in finding the variance of the composite? Since the variance of the composite for two items is the variance for each and the covariance, should i just add 121 + 33 + 23 to find the variance of the composites?

Inter-Item Covariance Matrix
Part1 Part2
Part1 121,046 23,106
Part2 23,106 33,215
I found out how to do this, if anyone else have this problem, the solution is just to go into "compute" and add the different variables into a single variable and then ask for descriptives and variance for the newly created variable.
So now I just need to figure out the difference between the alpha you set prior to looking for significance and Cronbachs alpha...