Hi Annie333
Welcome to the forum.
You might want to have a look at the following FAQ which explains where everything is;
www.benefitsandwork.co.uk/guides-for-claimants/faq/forum.
Your workcoach is correct, you need to give your workcoach a 'fit note' this starts your assessment phase, the assessment phase lasts 13 weeks, this means that when you are sent the WCA form called a UC50, if you are successful your claim will start from the 14 weeks when you handed in your fit note.
I would advise you to make a note on your journal when you hand in your fit note, it will then give you a timeline if there is any problems in the future, also take a screen shot with your phone.
Gary