The add-ins are integrated into Outlook, and so become a part of Outlook. Look for the Sperry Software tab in the main Outlook window:
Sperry Software in Outlook 2013 toolbar

If you don't see this tab, there could be several reasons why:

1) Make sure it is actually installed via Control Panel...Programs and Features...Uninstall a Program

It's listed under "Sperry Software - name of Outlook add-in"

2) Make sure it is the correct "bitness"

The tab might be missing because of mismatched "bitness" - that is, a 64-bit version of the add-ins was installed into a 32-bit version of Outlook. This article can show you how to tell if you have 32-bit or 64-bit Outlook, but the simplest thing to do in this case is to uninstall the 64-bit version, then download the 32-bit version and install that.

3) Make sure it is not disabled because of any performance issues

The add-in may not be visible because it may have been disabled - Outlook protects itself by automatically disabling add-ins that are causing performance issues.  It normally takes five Outlook restarts before this happens, so it's especially applicable if the toolbar was there before and now no longer is.  You can check to see if it is disabled by going to File...Info...Account Information:

  At the bottom of the right hand pane there are several icons for example Automatic Replies (Out of Office), Mailbox Cleanup, Rules and Alerts and possibly, a Slow and Disabled COM Add-Ins button.  If it is present, click it:

Notice that the "Sperry Software Outlook Add-Ins Engine" is listed.  Click Always Enable to allow the add-in to always run.

To prevent this problem from happening in the future, you can download the Prevent Add-In Disable tool.  It is highly recommended to download the tool, then right click on it and choose Run As Administrator, then follow the prompts.

4) Make sure .Net framework 4.0 (or higher) is installed (again via Control Panel...Programs and Features...Uninstall a Program)

This problem most frequently occurs if the machine was recently rebuilt, and/or any of the Windows Server editions of the operating systems are in use (which don't normally download and install the .Net Frameworks).  You can download the Microsoft .Net Framework from here.

5) Make sure that anti-virus and firewalls are temporarily disabled

Some anti-virus programs are stricter than others, and so do not allow installations to succeed.  Try temporarily turning off anti-virus and/or firewalls and installing again.  Make sure you don't forget to turn it back on once it's up & running.

6) Make sure that Outlook and Windows are both up to date

You can check this by going to your Start Menu and click on Settings...Update & Security settings...Windows Update. Here, press on the Check for updates button. If any updates are available, they will be offered to you.

7) The add-in may have become disabled due to a new Outlook or Windows Service Pack.

A new service pack may have knocked the add-in out of commission.  Because it could be due to an office or windows upgrade, try a clean reinstall.

8) Make sure the add-in is actually installed according to Outlook (in Outlook, go to File...Options...Add-Ins)

The add-in may be installed, but not loaded.  If that's the case, then it's a different problem entirely.  Luckily, we have an article on how to correct the error "Not loaded. A runtime error occurred during the loading of the COM Add-in."