Hi ,
The simplest way to update to a newer version of the Engine would be to delete the existing Engine folder from your computer, then reclone the newer version with the correct dependency files for the newer version. This is not recommended if you have modified any of the Engine source files.
There are other methods for updating to a newer version of the Engine, but they are a little more involved. I can expand on one or two of those methods if you would like.
Alternatively, you could try downloading the 4.2 version of the Shooter and Strategy games and open them in your current Engine version. It is possible to upgrade a project from 4.2 to 4.3, for example, but you cannot take a project the other way (from 4.3 to 4.2). Even when upgrading a sample project from 4.2 to 4.3, you will still need to go through and clean up some code errors caused by changes to the Engine, so downloading the correct version of the sample project is usually the easiest option.