Visit the ImageMagick downloads page and grab a binary. If you have a 64-bit Windows installation (Subsection H.1.4), use the recommended version. If you have a 32-bit installation, find the version whose filename is obtained from that of the recommended version by substituting x86 for x64. For example, if the recommended version's filename is:
then a good choice for a 32-bit Windows would be
Congratulations, you have successfully installed ImageMagick.