Add the ClockIt bot to your Google Chat by clicking in the + button next to bots.
Search for ClockIt and then click on Add
Next you will need to login. For this use the command @clockit sign in and you will get a configure button.
Click on configure and sign in with your ClockIt account credentials. Accept the permissions and you are now connected.
To clock in using Google Chat simply use the command @clockit punch. To clock out use the @clockit punch again.
To know the status of your punch use @clockit status.
To sign out use @clockit sign out.