It is not possible to merge accounts. You will need to export your space(s) from the account you wish to close and manually import it/them into the space you are keeping active.
Do I need to input credit card information to start my free trial?
No! You can start your 14-day free trial just by registering and selecting the free trial as an option. When your trial ends you can choose to input your credit card information to upgrade and keep benefiting from Capacities Pro, and if you choose to let the trial lapse, you will not be charged.
How can I remove all existing content in Capacities and start again?
The easiest solution is to delete any spaces with content in.