Summarize:

Shake through to cover in salt. Place in the fridge and leave. Stored in this manner, the basil leaves will remain in great condition for use over the coming months. Both the leaves and the oil (now infused with basil) can be used for cooking.
Clean the basil leaves and allow to dry. Place in a suitable storage container. Sprinkle with salt. Fill the container with olive oil. Cover the container. Use as usual according to your recipe.