Newbie, need help with deposit pls

Tenancy Deposits

Hi, please forgive my ignorance, if this is possibly going to be the most stupid question out there? I have only very recently joined the RLA as before i have used an estate agent to let my property of which they did all the work for me, so this is all completely new. I have a tenant wanting to move in on 1st May, and i am getting her deposit of £200 from her next weekend. I have used the documents on this site to set up a Assurent shorthold tenancy agreement. But i just wondered what do i actually do with the deposit of cash that she gives me for the deposit. What is the process and where is the money held????

Many thanks for your time,
Sarah.