Google provides extensive documentation on using Gmail.

Some of the specific questions we have been asked are listed and answered below:

• How do I send an email to a list of addresses in a spreadsheet?
  To upload a spreadsheet of contacts, it needs to be saved as a .csv file. This means a "comma separated values" file as opposed to an Excel file. You can mark this when you go to "Save As" and use the drop-down box to change the type of file.
  Here is a weblink to show you how to create a CSV file: https://support.google.com/mail/answer/12119
  That's really the trickiest part, because importing it into Gmail is easy. Go to Contacts (by clicking the arrow next to "Mail") and then there is a button with the word "More" on it. Clicking "More" will give you options including "Import." You can then choose the file.
  For a step-by-step import tutorial straight from Google:
  https://support.google.com/mail/answer/14024
• How do I create a contact group?
  
  Google's instructions can be found at: https://support.google.com/mail/answer/30970?hl=e
  Note that the group will be created within the "My Contacts" section of your address book. When trying to add people to the group, you will probably want to search for the person and then use the Groups button drop down, shown below, to choose which group/s you want the person in.