By default, when you sign in your Gmail account, you will see Hangouts at the left-bottom corner. However, you can decide whether to show the chat window or not.
Step 1: Login your Gmail account (please refer here to open one if you do not have an account yet);
Step 2: In the Gmail account, click the "Setting" button from the right-top corner;
Step 3: Click the "Settings" command from the drop-down list;
Step 4: Click the "Chat" tab in the settings menu and click "Chat off
" if you do not want the chat window appear;
Step 5: Click the "Save Changes" at the bottom and the chat window will disappear;
Step 6: To bring it back, repeat the steps above and click "Chat on".
You can also bring the chat window to the right, please see here for details.