Can I use www before my address?

[Andrew]

Yes, using www works both for domains and sub-domains and you can choose which you'd like to use in your links and more.

For instance...

www. you.example.com & you.example.com will both load the same site you.host.com

- or-

www. yourdomain.tld & yourdomain.tld will both load the same site yourdomain.com

Tip

For both simplicity's sake and for good SEO, you should choose to use either one or the other in your links, the best option would be to drop the www which also results in better loading times for your site.