From the Finder's Go menu select Go to Folder. Enter /private/etc/ in the field and click on the Go button. If a hosts file is present you will see it listed and can edit it per your instructions. If one is not present then use any editor to create a file and save it as hosts with no extension.
You can use TextEdit to edit or create the file. You can also edit it using the Terminal application in the Utilities folder by entering the command, pico, at the prompt and pressing RETURN. Pico is a simple editor but will do the job. If you find it gives an error then try, sudo pico, instead. You will be prompted for your admin password that is not echoed to the screen.