Do you mean writing funding applications for trusts and foundations? Do you have a voluntary sector background? Have you been writing applications in your previous role? If so then I would start by approaching your contacts. If not then it's going to be harder to persuade someone that you are the right person for the role and you'll need a good understanding of the voluntary sector and be able to ask the right questions of your clients to get the right information to put the application together.
You should be fairly well placed so long as you've a really good understanding of evidencing need, getting your head round projects and being able to show outputs, outcomes and impact. If you've never done funding applications before maybe link up with T&F contacts and see if you could perhaps do a couple of draft applications and then ask them to look them over. It's very different to community fundraising so might also be worth getting yourself on a few courses. If you haven't already done so then get yourself on the Lottery website and have a look at their various programmes to see the kind of questions they ask.