Mediation with Regression Analysis Need Help some basic Question (Using SPSS)

I have 3 variables (2 are independent and 1 is dependent). All three variables are measured with questionnaires consisting of multiple questions recorded on 5 point scale. I want to perform regression analysis to check for mediation. How do I go about doing that? Do I have to transform or recode variables? My variables are explained below

Creativity = Q1 + Q2 + Q3 (Do I need to transform Q1-Q3 into single variable representing all three q's of creativity to run regression; if so how to do that?)

Climate = Q1 + Q2 + Q3 + Q4 + Q5 + Q6 + Q7 + Q8 (Q1-Q8 into single variable)

Motivation = Q1 + Q2 + Q3 (Q1-Q3 into single variable)

All the questions (Q1, Q2, ...) are measured on a 5 point scale, 1 for strongly disagree and 5 for strongly agree. I want to run below model.

Creativity = constant + β1 Climate + β2 Motivation + error

I am using SPSS.