This is the addon you need to install from the playstore:-
https://play.google.com/store/apps/details?id=com.teamviewer.host.market
I always download from the playstore as you get automatic updates.
As well as installing the above app on your parents box, I assume you have registered a free account with Teamviewer from your laptop which will mean you have a Teamviewer user name (your email address) and password, which you will be asked to input when you run Teamviewer Host on your parents box.
Login to your Teamviewer account on your PC/Laptop.
When you run Teamviewer Host for the first time you will be asked to install another Teamviewer App app, do that.
Then input your Teamviewer login details.
You will be sent an email asking you to add your parents box to your trusted devices, do this.
Then back to your parents box and select assign.
You should now be connected and in control of your parents box.
The benefit of using Host is that having done the above successfully once, your parents box will be in your Teamviewers trusted devices and you will be able to connect remotely without your parents doing anything, other than having the box switched on.
If you have Teamviewer Quick Support App on your parents box, you can connect using that app, just your parents will have to initially be available at their box to run quick support and work with you to make the connection.
If I find a clear set of instructions/video online I will post it.