if the hook already exists, there's a simple solution.
add them in the database.
first search for the module id for the module you want. that would be on table ps_module.
then search for the id of the hook you'd like to hook the module to. it's in table ps_hook.
then once you have all that information it's just a matter of adding them to the proper table, ps_hook_module
if you have more modules hooked on that same hook, you'll probably need to check the position. not sure if putting position 1 to that hook, when you already have another one on that position will cause any problems. it's a bit time consuming but it's sure to work.
Click on the ps_hook_module, then click "insert"
and enter the id_module
id_shop (should be 1, unless you have multi-store)
id_hook
position
click go, and enjoy