new kitty

I have brought a young male cat, Minion, inside to live. Minion had shown up in the fall and never left my porch. I've always put food out for strays so decided to adopt Minion as an outside kitty. But as time went on, I observed how sweet and docile Minion is. Whenever another cat came around, Minion ran and hid. When my area got hit with the polar vortex, Minion came inside to live. It has been so wonderful having Minion inside! He is so playful and snuggly and adorable  😍

Unfortunately, my older female cat, Stormy, is not so smitten. Stormy is around 8 years old and neutered. There has not been any actual fights, just a lot of hissing and some "whapping". And ambushes, lol... unsure how my fatty Stormy hides her girth to ambush the little one but she managed somehow.

So, anyway, does anyone have any tips to socialize my 2 cats? Minion gets along with everyone; Stormy gets along with no one  🙄  Any advice is appropriate because I'm new to having multiple cats.