Generalized linear models are fit as a personality of the Fit Model Dialog. After selecting Analyze > Fit Model, select Generalized Linear Model from the drop-down menu before or after assigning the effects to the model.
When you specify that you are fitting a generalized linear model, the Fit Model dialog changes to allow you to select a Distribution and a Link Function. Options for Overdispersion Tests and Intervals and for Firth Bias-adjusted Estimates also appear. In addition, an Offset button is added to the Fit Model window.