After Mavericks reinstall, no admin password set??

I'm helping friends who lost their Mavericks admin password, and hence could not install new software, etc. We reinstalled the OS successfully -- but were never cued to set a new admin password. We were able to install a couple of needed programs afterward without being asked for a password. Is this normal? Do we need to set a password, and if so, how? Or can we rely on being able to continue to install new stuff, etc., without a password?

(I only succeeded in posting this by identifying the OS as 8.3 in the "Identify Your ...Operating System" pull down, as that was the most recent system ID offered. Odd that Apple support forum doesn't keep up to date on Apple's own OS.)