Hi, and welcome to the Forum, the best on the 'Net!
For novices my advice is to download and install click here
then run the One-click Maintenance, you do not need to make any changes to the settings. It will only take a minute or three, then click on the Repair button.
This is a grreat program to run on a weekly basis, and will generally keep your PC running smoothly - though not the be all-and-end all of programs, nevertheless well worth having, especially as it is Free.