Boot stretchers like FootFitter 2-Way Shoe ... but wearing thick socks to fill out your shoes can also help soften the leather so that it stretches out. If you're able to manage wearing thick ...

Gently wipe the entire leather surface with a clean towel or use a soft brush to gently remove dirt. Apply a natural oil such as a spoonful of coconut oil, lanolin, neatsfoot oil, mink oil ...