You will need to compile it yourself and install it in your home directory.
Download ctags source: http://prdownloads.sourceforge.net/ctags/ctags-5.8.tar.gz
In hour shell:
$ tar zxf ctags-5.8.tar.gz
$ cd ctags-5.8
$ ./configure --prefix=$HOME
$ make && make install
This will compile and install ctags in your home directory. The resulting binary will be: $HOME/bin/ctags
You will now have to modify your PATH environment variable prior to launching vim.
$ vim $HOME/.bashrc (or whichever shell you're using)
put this line in your .bashrc
You will now need to resource your .bashrc (remember that .bashrc is normally only loaded from non-interactive shells. Make sure that you source .bashrc from .bash_profile)
If you need to, modify your .bash_profile and make sure it has a line like:
To continue without closing your shell, simply type:
$ . $HOME/.bashrc
You can now launch vim and ctags will be working.