How to Archive mail and unarchive in Gmail ?

To archive messages:

1. In your inbox, select a message by checking the box next to the sender's name.
2. Click Archive. (If you have a message open, you can also archive it by clicking the Archive button.

To move an archived message back to your inbox, follow these steps:

1. Click All Mail. (If you don't see All Mail along the left side of your Gmail page, click the More drop-down menu at the bottom of your labels list.
2. Check the box next to the sender's name.
3. Click the Move to Inbox button.