You can change “Sign In link position” to Top bar in Theme Options > Header > Header layout and add a Text widget with the content in Appearance > Widgets > Top bar area.
If this is not what you are looking for, please describe the desired result in more details.
There are 2 ways:
1) You can enable Top bar and use the top bar widget areas to add content you need
2) Copy the xstore/header/xstore.php file to your child theme and edit content according to your needs http://prntscr.com/mlgl6k