I am a complete newbie to sublime so this question my seem a bit silly! After I have loaded a package into sublime text 3 how do I open it and begin to use them??
Each package is used in a different way, you will need to read the package documentation. Some of them are passive, some have shortcuts you can use while others may add commands to the command palette (
Ctrl + Shift + P) among other things. You may find information about the package in
Preferences -> Package Settings