Rebuilding array due to failed drive

Thanks for reading. We've got an older MD3200 which has been running some file shares. One of the drives failed late last week. We have replaced the drive, but the array did not start to re-build immediately. Instead the replacement drive is indicated as "unassigned" in the array. We're not sure if we should assign the new disk as hot spare and allow the array to adopt it, or if we should proceed to another option. When investigating the hot spare option, we're presented with a few choices:

view/change current hot spare coverage

automatically assign physical disks

manually assign individual physical disks

We've tried to engage Dell support, but the hardware is EOL/EOS and we weren't able to connect with anyone. We're just hoping for some guidance before we move forward, so that we don't lose the data on the disk or array. Appreciate any help.