OK, this is something you can simply do yourself, to check permissions:
On the dock at the bottom, click the icon to the far left, the smily face aka ‘Finder’.
A window will appear, in the left hand column, select ‘Applications’
Scroll down to a folder called ‘Utilities’, in there will be an icon called ‘Disk Utility’. Double click it to launch the application.
A new window will appear. In the left hand column you should see an icon for your hard drive called ‘Macintosh HD’
Click it once to highlight it
In the right hand side of the window, across the top, there are 4 tabs, click the one that says ‘First Aid’
Now, at the bottom there should be a button called ‘Repair Disk Permissions’
Click that, and let it’s churn away – it’ll fix any permissions problems.
At the end it’ll give you a report of any issues it’s fixed.
Once that’s done. Restart the machine.