DMG installation on Mac OS X

I downloaded the software on to my macbook air. It remains in the Downloads folder. It is not getting executed/run as an application and coming up in the launchpad. Whenever I click on the .dmg file it opens in the disk utility as an external disk. Is this normal?

Yes, it’s normal. You should drag & drop Manager from “external disk” to your desktop or dock. It’s how most Mac programs are “installed” as far as I know. Manager is no different.