Logisitic regression in SPSS


I'm trying to calculate logistic regression in SPSS, in order to indentify predictors to successful treatment group.

so my dependent variable is: treatment success (categorical variable)

and my covariates are:
1. age (continuous variable)
2. anxiety score (continuous variable)
3. depression scores (continuous variable
4. age group (categorical variable)

My questions are:
1. Should I run the test several time with each of this covariates by itself. Or should I run the test with all these covariates together

2. do I need to specify in the spss logistic regression dialog box that covariate 4, is a categorical variable?

Thanks a lot.
and don't forget to specify your reference category

Don't forget that when you specify the one variable as categorical, SPSS will automatically suppress the last category as your reference category unless you tell it otherwise.
you also should state the method of entering the variables, stepwise, forward, backstep or enter...each has a different way of entering the variables accordingly.