Your will sets out what happens to your estate after you pass away. You can say what you would like to happen if you become so unwell you can’t deal with your affairs when you are alive too. This needs a separate document: you will need a Lasting Power of Attorney.
You can follow the government guidelines on making and registering a power of attorney. Some websites offer this service as a paid for extra however if you can make a will online then you can probably make a power of attorney online too.