Questions about login to the Apple store and finding an application once installed

I've only had the MacBook pro for about 10 days, after converting from years of abuse from Windows. I purchased a refurbed Macbook Pro, 8.1, with a new 1TB sshd, and 8 gigs of ram. It came with what I think is a fresh install of Sierra. Today when I turned it on I was notified that updates were available. I have an account with the Apple store and ICloud that I set up last week. I logged into the store and said update all. After 12-14 minutes the computer restarted and all was fine. Everything seems to work, something that was not always the case running Windows 10 on a PC. About 5 updates were installed, such as a Sierra update, printer software update, etc., but I noticed one more up needed to be installed, I think it was called garage band. I clicked update garage band. The computer ask me to log into the Apple store, but the ID was someone else's email address. I told it I forgot my ID, it gave me several options one of which was to reset my password for the store. I did this and tried to update the garage band. Same thing happened. I've had to change my password to the store 3 times in 10 minutes because the store thinks the computer still belongs to the last person who owned it. I don't understand why the store keeps saying the computer belongs to a different email address especially since I signed into the store last week and downloaded several free apps. This only seems to happen when I try to install this last update. How do I stop this other person's email from coming up in the store login when trying to download an update?

Second question. I downloaded coconut battery several days ago. I cannot find where to start this app. When I look under utilities, launchpad, applications, or dashboard it is not there. I can make it run by clicking on Siri and saying "open coconut battery". There has to be a way of seeing where this app is installed and starting it via the icon rather than speaking into Siri.

Hi Carroll. - at the moment, I'll not address your first question, but you might want to look at this Apple KB Article to determine if the seller did the steps listed there.

As to Coconut Battery - go into Finder -> Applications - the app icon should be there (see first pic below); or hit 'Launchpad' in the Dock - the app should also be there - I put it in a Utilities folder as shown in the second pic. Dave
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Dave, the icon for coconut is not in either location you show yours in, that's what puzzles me. How can it not be there and yet run with I tell Siri to open it? Crazy thing was the icon for coconut was one the right side of the dock, next to the trash can and listed as downloads. I clicked on it and dragged it to the applications folder and now the icon is there and I can open the program by clicking on the icon.

When you get a second hand computer always erase and format the hard drive and do a clean install. Sounds like your problem is the User Account is still set up with the former users details and when you go to the App Store it is picking that up, as Dave's link addresses.

Another place coconut could be hiding is in the downloads folder. Click on the Finder, smiley face extreme left of Dock, if need be click the Users little arrow downwards and a list of folders come up including Downloads. It will be hiding in there. If the computer was not wiped, there could be a whole host of the former owner's Documents etc.

To clear the mystery, Coconut Battery was in Downloads all along, never got installed. Siri finds it because Siri uses Spotlight to find things and Spotlight had indexed it in Downloads. Mystery solved.