First you will need a good small spatula.
Make sure you have cleaned and dried the surface throughly.
Put a small blob of the paste on the area and use the spatula to spread out to the edges, making sure it’s a covering the surface as even as possible. Always start with a small amount of paste, because you can always add more if needed, but it’s a bugger to get rid of excess without having to start from step one again.
one school of thought has you putting the paste on both surfaces, but that can end up having too much in some cases.