Install the latest version of Internet Explorer, Google Chrome or Mozilla Firefox in your computer, as they contain plug-ins or add-ons required to run the Gmail chat program online. Visit Gmail website and create a new account, if you do not have one already. Click the "Create an Account" button on the Gmail’s official page and you will be taken to the account creation page.
Fill out the form with all the necessary information and click the "I accept Create my Account” button at the end of the form. You will then a confirmation message on screen about your new account creation.
If you do not have AIM installed in your computer, then you will have to visit AIM’s official website and download the latest version of the messenger program. Once the download is complete, run the installation file and follow the onscreen prompts to complete the process. Also, create a new AIM screen name and password to get started.
Now open your Gmail account and open the “Chat” option available at the left side panel of the screen. If you do not find the “Chat” option, then you should make sure that you did not enabled the "Turn off Chat Gmail View” option, appearing at the bottom of the page. If it is checked, just uncheck the box appearing against it and you will signed in automatically to Gmail chat.
Right next to your status message on Gmail chat, you will see an arrow. Click on it, and select "Sign into AIM”. You will now be required to enter your AIM screen name and password, to integrate it with Gmail. Once the setup is complete, you will not have to provide your screen name and password on next login. You will now be able to see your AIM contacts in Gmail chat.