Smell it.
First things first, take a big whiff. You know what I mean. Like you're checking to see if it's you that has B.O. Leather smells great, take it all in!
Fill it up, slowly.
Take it easy when putting cards into your new wallet. It'll stretch over time, but you don't want it to blow out. If you fill it with too many cards per pocket, it'll stretch too quickly and then the cards may become loose! Try to only use the cards that you absolutely need at first so you don't stretch it too quickly.
Mind the water.
Try not to get it soaked. It's not going to be the end of the world if you take it for a quick dunk in the pool or spill some water on it. It might lead to premature wear on the leather. Make sure you let it dry afterwards and you can always apply some balm like Smith's Leather Balm. A little goes a long way with it so use it sparingly.
Use it.
Use the damn thing. It'll wear in great. Leather takes on what's called a patina. The oils from your hands, the friction from fabric and even the sunlight will help darken and give your leather character. That process is called a patina and it'll make your wallet unique to you and your journey.
If you treat it right your new wallet will last a long time. Each and every one of them is hand-stitched by me.
Set Sail,
Ruben