Modify watermark through the css

Hello guys, i wanted to modify the water through the styles.css given by VF :

/*
FOOTER

Customize the layout and appearance of the message input field and the VF Branding
/

/ .vf-footer {} /

/ .vfrc-input {} /

/ .vfrc-chat-input--button {} /

/ .vfrc-footer--watermark {} */

i have no idea how to modify the text nor integrate a link VF does with the default watermark.
I appreciate any help