remove the inner boot clamp. The boot will then allow a small insertion device to add the oil between the axel and rubber boot. Do not inject oil through a small hole you make in the boot.

I have heard a turkey baster will do it as well. Very large syringe with a small rubber tube attached may be the best as already mentioned by another member.

I like the ideal of going to the druggist to ask for a syringe. I always needlessly explain that i am not a junkie. They are cheap as well. Also I use them as precision oilers on occassion as well as for critical glue injection in small spaces. Removing the very sharp point first by grinding it down. I would hate to stab myself.

If you find a boot under there that is leaking. The axle should be removed and the leaking boot changed or another axle with good boots installed.