I guess you have problems figuring out the relation between antenna size and wavelength: The usual "prototype" antenna is a 1/2 wavelength dipole, which resonates nicely on received frequency. It's most konwn brother is 1/4 wave antenna, where the ground side substitutes the other half of the 1/2 wave dipole. In general, good antennas very often have a maximum dimension, which is a significant fraction (or a multiple of) wavelength. That would usually make for example 100km wavelength half-wave dipole impractically long.
However, an antenna CAN be much smaller than the wavelength, and still work pretty well. The antenna efficiency might not be as good as for larger antennas, but performance for given size can be reasonable.
One common technique for very low frequency antennas is using so-called loop antenna, which connect mainly with the magnetic field component. Other techniques exist as well, including simply accepting a reduced efficiency, using added coils, or high dielectric constant materials. Or even using the environment, such as seawater for a submarine application, as part of the antenna system.
As Audioguru already pointed out, using Google and Wikipedia will give you a lot of useful information - as in a discussion like this it is impossible to present everything of such a large subject as antennas.