Click on the Google Apps Icon right next to your Gmail profile picture.
3
Click on the contacts app.
4
On the contacts app, search for the contacts you want to include in your distribution list in Gmail.
5
When you have selected the contacts you want to add your distribution list in Gmail, search for this label icon on the top of the page.
6
Click "Create label" and name your distribution list. When you are ready to compose an email, in the "to" field, type the distribution list name and Gmail will automatically send your email to the contacts there.