Pour the base stain into a plastic container. Then slowly add the second stain while stirring with a paint stirrer/wooden spoon until you think it is the right shade.
Mixing stain is very easy to do. Be sure to mix all stain well before starting. Using a child's medicine syringe or similar item, measure out each stain you want to use. Mix together well and apply.
There is a product called "stain components" that allows you to mix your own stains. You can also buy a clear stain base and a colorant. Most home supply or paint stores will have what you need and will help with mixing.
