If you are going to use your HOSTS file often, I recommend you use this tool.
As you see in the screenshot above, the add button can let you add the sites you want to block. You can add, delete or temporarily disable the items with this tiny tool.
Then, saving the HOSTS file over the original can be performed without having to verify your admin credentials.
If you still can't save to the HOSTS file location, you probably don't have the correct permissions to be editing files in that folder.
For example, you can block websites using just the HOSTS file.
All you do is add your own DNS lookup and you’re good to go.
In fact, blocking websites through the HOSTS file is an effective way to do it because it blocks it across all the browsers (we’ve previously discussed methods to block sites in Internet explorer and Google Chrome).