Heat the boots up with a blow dryer and apply wax from a johnny ring. Yea, the seal for a toilet bowl.  Heat again for the wax to penetrate.

Don't do anything, yet!

When waterproofing leather, among the things you need to be aware of to use are:
1. Vegetable tanned, or chrome tanned?

2. Smooth, or rough out?

3. How is upper affixed to midsole?

4. How many seems in upper?

5. Full grain leather upper, or split leather, or suede?

6. All leather upper, or leather-synthetic?
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Visit REI's boot repair shop in your area, or a hiking boot repair shop. Shoe repair shop may not be sufficiently expert in nuances of waterproofing.

If you use an incorrect/inappropriate compound, your boot will deteriorate much more quickly than it should. There is a possibility that the wrong compound will exacerbate letting moisture into the boot rather than retard it.
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Having written that, if you wear cheapies, do what you want. If you wear [traditional] Italian or Swiss hiking boots with Norwegian welt, you would be foolish to not treat them well.

Hope this helps.

I have those same boots, which came new several years ago advertised honestly as "As waterproof as leather can be." For all leather I use Montana Pitch Blend, multiple coats melted in and buffed between coats. Nothing better and the all-natural scent doesn't spook game, at least not elk!

Obenaufs for me

I have never found mink oil to waterproof anything in fact it washes off with water.. I use snoseal.. 1st heat up the boots in the oven at about 150 degrees then just rub it in... You can also use parafin if you heat the boots up 1st