first thing i would do is analyze the look of an older photo that you like – are the colors saturated? is the black really black? is there a lot of contrast? is the white balance warm or cold? to get the look of old photos you have to match the look that you like. drag a photo you like into the one you’ll be modifying. put them side by side and try to match the look and feel by adjusting curves, hue/saturation, levels, adding noise, etc.
https://www.youtube.com/graphicsdump
https://www.myr3d.com