The fontenc and inputenc packages are installed automatically in every base LATEX distribution.
All the necessary extra files to use with these packages for Cyrillic
are in the cyrillic bundle, which at present contains the
following: four font encoding definition files (t2aenc.def,
t2benc.def, t2cenc.def, x2enc.def); several input encoding
definition files (all the other *.def files), and font definition
files (*.fd).
The installation of these is described here.