You can enter the Faeries realm by Astral Projection. Fairies realm is a non-physical dimenssion, which means you have to be able to visit the spirit world; you do that by mostly Astral/Etherial Projection.
I don't think a spell can help you to that.
The "realm" of the Fae is figurative in the same way you use "underground" to describe something illegal or unofficial.
Think of their realm as a sort of territory marker as in the Fae territory. With that you must understand how broad of a term it is as the word "Fae" these days basically refers to any kind of living creature (the culture of its origins hardly matters) not described by scientific taxonomy. Which yes, includes more than just Tinkerbell.