If you want Gmail to open when writing an e-mail from CentralStationCRM instead of your default email program on your computer you need to adjust a few settings:
First you need a two small extensions for your (easiest: Chrome-)browser. Afterwards you can create new e-mails directly in GMail and have them put in parallel in your CentralStationCRM account.
The first extension is called "GMail Notifier", a small program that will open the e-mail links in Gmail. But, however, the BCC address isn't auto completed. Therefore you need a second extension called MailTo for Gmail.
In the Gmail Help you find an explanation to this add on.