If you are going to start from scratch and apply a new config anyway, I would suggest that you clear the config on both ASA, and copy the config the running config to ASA-1. Because otherwise if you copy it to start-up and reload the active ASA, the other unit will become the active, and will override the configuration. Even though the standby unit does not become the active unit, if you have a totally different configuration on ASA-1, then it would become a mess as the 2 configurations are different.
If it's a brand new configuration, then i would suggest uploading the config to the primary ASA start-up, then "write erase" both current config, reload both ASA. The secondary ASA needs to be configured with a few failover command, and primary ASA will automatically sync the config once secondary ASA has been configured with those failover comamnds.