The standard workflows that ship with EPiServer are not very customizable (just examples of each type of workflow). You can only change some of the labels in the notification email by editing /lang/workflowFoundation_EN.XML (or whatever language), see http://world.episerver.com/modules/forum/pages/thread.aspx?id=3355.

In order to fully customize the content and layout of the email you should look into building a custom workflow:

http://world.episerver.com/Blogs/Andreas-Ek/Dates/2009/3/Workflows-with-EPiServer-is-really-easy/

http://world.episerver.com/Blogs/Hans/Dates/2012/4/EPiServer-Workflow-Replacement--Step-1Explanation-and-Disabling-Edit-Tab/

http://www.markeverard.com/2010/09/29/developing-a-custom-workflow-in-episerver-part-one/

Thank you for your answer, but is there a way of modifying the link or adding another user?

The emails are standardized and hardcoded in the workflow, so no, you cannot easily modify the link in the email.  

That's why I suggested you look into building a custom a workflow, where you can make your own SendMail event and definer the email however you want, as described here: http://world.episerver.com/Blogs/Santosh-Achanta/Dates/2013/1/Tailoring-workflows-for-EPiServer-5-6-and-7/

Code for EPiServer 6 workflows can be found here: http://world.episerver.com/Blogs/Johan-Bjornfot/Dates1/2011/8/Source-code-for-the-CMS6R2-built-in-workflows/

What do you mean by "adding another user" ?

In the workflowFoundation_EN.XML file can i add a text or a link, e.g saying "please use the following url: xyz" as oppose to the generated link? is this possible?

You can change the text in any of existing nodes in workflowFoundation_EN.xml, but you can't change the generated link since this is hardcoded in the workflow.

Like I said, you will need to make a custom workflow to achieve want you want.