Because SOPAC is a Drupal module, installation paths will vary from system to system. You will install and enable it as you would with any other third party Drupal module.
It is strongly recommended that you purchase a SSL certificate for your Drupal site. SOPAC has the built-in ability to encrypt pages appropriately and will take advantage of your encrypted server.
Configuring Apache2 for SSL support is beyond the scope of this guide and there is plenty of instruction and support available on the web.
You will, however, need to make the following addition to your SSL virtualhost definition (just the SSL definition, not the regular one). Your enabled SSL site should be encapsulated in a definition that looks like this:
<VirtualHost 1.2.3.4:443>
...
<VirtualHost>
Within that definition, put the following line:
SetEnv HTTPS TRUE
SOPAC/SSL integration will not work unless this parameter has been properly set.
Once you have succesfully installed the SOPAC module, you will want to tailor it to your environment. SOPAC makes this very easy for you.
First you will need to set the appropriate permissions. They should look something like this:

Next, visit the SOPAC configuration page under Administer > Site configuration > SOPAC Settings (or /admin/settings/sopac). You'll notice that there are three configuration sections. The first contains the critical elements that must be correctly set:

You can choose to tweak the settings in the other two sections now, or wait until later.