Here is what it should look like in windows explorer:
Note, you may have to change ‘permissions’ on that folder to allow hidden and system files to be shown.
The file can be edited with a text editor.
Before it can be edited and changed, however, it needs to have its permissions changed from ‘read only’
It could be the case that running notepad as an administrator negates this neccessity.
Don’t worry about the size of the file- Some are larger than others due to customisations of ip addresses/ urls blocked by the end user post windows installation. Spybot Search & Destroy is an example of a program that some users run to edit their “hosts” file to block certain known dangerous websites. As a consequence of this sort of ‘protection’ some ‘hosts’ files are significantly larger than others.