Yes, you can sign up and have this option ready for you when you do need it. You will need to connect your accounting software, pass our Anti Money Laundering checks and agree to our terms, but you have no obligation and pay nothing until you start using our service.
It can sometimes take a little while to onboard, for example if further information is needed, so if you think you might want finance in the future it's a good idea to get set up before you're likely to need finance.