Total Newbie

Hello! I just bought my first road bike about two weeks ago. I am a fish out of water but have NEVER been so hooked on something ever! That being said… I need some help figuring out what I’m supposed to be doing training wise. I really want to be able to get to the point where I can hope on the bike and really ride. I live in SoCal so flat areas are few and far between. I am still in the trial and error portion of learning how to tackle hills. I also am using flat pedals until I have a little more confidence for clip ins, although is that a mistake? Any and all advice is welcome!!

Some minor background on my current abilities:

• I can ride for about 20 minutes before I’m gassed. My route has very minor elevation changed but it just zaps me so fast because I’m so out of shape.
• I own an echo bike that I can go for about 3 miles on before I’m gassed.
• I have a gym membership with stationary bikes that I have access to.
• I am on a used bike that is incredible, and own a good helmet and bib shorts.

Thank you in advance!!