Computing Scales/Subscales

My dissertation (psychology) is on the relationship between social connectedness and psychological distress. Essentially, I am combining 9 scales that broadly reflect social connectedness (loneliness, alienation, solitude etc.) and measuring them against the DASS21. Before I attempt my main analysis I have to reverse score some items.I also have to compute all necessary scale and subscale scores (means or sums depending on what is recommended) and compute Cronbach's alpha for all scale and subscales. I definitely know how to recode variables but the rest I am not too confident with. If someone could direct me to a site/paper that may help me understand this further I would be very grateful. Thank you