ArrayTools can be installed as any other offical Julia packages:

… pkg> add ArrayTools

where … pkg> represents the package manager prompt (the ellipsis denote your current environment). To start Julia's package manager, launch Julia and, at the REPL of Julia, hit the ] key; you should get the above … pkg> prompt. To revert to Julia's REPL, just hit the Backspace key at the … pkg> prompt.

To check whether the ArrayTools package works correctly, type:

… pkg> test ArrayTools

Later, to update to the last version (and run tests), you can type:

… pkg> update ArrayTools
… pkg> test ArrayTools

If something goes wrong, it may be because you already have an old version of ArrayTools. Uninstall ArrayTools as follows:

… pkg> rm ArrayTools
… pkg> gc
… pkg> add

before re-installing.