How do I install it ?

The package is build with the GNU Autotools. So a simple
./configure
./make
./make install

should do it. Also see the INSTALL file in the package.
You don't need any special privileges and can install it everywhere, although you should
be able to write to /var/lock.

But don't expect to much. Since I recently read the documentation
for GNU Autotools especially for mlencr the package lacks
proper dependency checks. So you will notice failure no later
than with the ./make step. Read also the FAQ entry "what dependencies
does the program have ? "