use some leather conditioner/waterproofer. theres a bunch out there. ususally easier to find it if you look for stuff made for boots. i like huberds shoe oil and shoe grease. also, theres snoseal, bear grease, many others.
treat it as needed depending on how much weather it sees.
i use this stuff on all my leather. jackets, pants, boots, car seats, mc seats. keeps it soft and pliable and very waterproof. i can ride all day and stay dry inside my leather with it treated or hike and walk right through water and feet stay dry.