I have an Optiplex 3020 desktop computer. It has its original 500G HDD hard drive, which came with the PC. I am running out of space. I would like to add an additional SSD disk. I opened the cover and I wasn't to figure it out. I am not sure how can I add an additional hard drive. I don't mind remove optical drive and replacing it with a 4TB SSD drive. Is it possible to add an additional drive? If yes, can someone guide me beside the SSD what else I need installing the SSD? I am a beginner if someone can mention all the steps for me. 

Appreciate your help!