Download PSI. Official website: http://psi-im.org/download. Windows users are recommended to download the Windows Zip Archive (2.96 MB) from the webpage, which allows you to use it without installation.
Chinese language installation package download: http://psi-im.org/download?page=download&version=0.10&lang_id=psi_zh
Instructions and help documentation: http://psi-im.org/wiki/Main_Page
Make sure you have exited gtalk, then run the main psi program. Click on the menu at the bottom left corner labeled "account setup" to add your gtalk account. Refer to the attached images one and two for settings of account and connect, then save.