How do I get rid of InstallMac?

I have been spared but try the site by Thomas Reed: http://www.thesafemac.com/arg/ there yo can find the adware removal guide & an app called AdwareMedic (donateware).

That should do it.

Apparently uninstalling InstallMac is a difficult one; see http://www.thesafemac.com/installmac-uninstaller-antics/ .

I met the same problem, but I solved it perfectly. If you delete an application by dragging it into the wastebasket, you leave a large number of associated files on the Mac, such as software caches, application preferences, saved status, and so on. So I suggest you use Mac Uninstaller in an application imymac, which can solve the above problems very well.

Step 1: On your Dock the 1st icon on the left should be your "Finder". Click on the Finder and a small window will pop up. (Will look like the picture below.)

Step 2: On the left hand side click on your Applications Folder.

Step 3: Then scroll down through your applications until you find InstallMac.

***If it is in a Folder open the folder...it may have a uninstall icon. If not go to step 4.

Step 4: Drag the InstallMac Icon or Folder to the "Trash" (Icon on Far right of your doc.

Step 5: Click on the desktop of your computer. On the top left next to the Apple Logo...It should say finder. Click on Finder and then you should see "Empty Trash"

Your Done....

TIP: I can't recommend enough a program called CleanMyMac. Run a google search and they offer a free trial. It's a safe application from a reputable developer. When you open the CleanMyMac App it has a Uninstaller button on left. The benefit of using this program is it will find any subfolders etc. any programs you've installed on your computer...has set up...sometimes there are a lot. CleanMyMac gets rid of all of these...Plus it does so much more.

Try reading this
http://www.thesafemac.com/arg-identification/