When you receive APeX access for the first time,

you will be given a generic temporary password.

The temporary password format is Uc$fMMDD

(where MM is the birth month and DD is the birth date).

For example, if you are born on June 7th, (06/07/XX)

then your temporary password will be Uc$f0607.

You should receive a prompt to change your temporary password, but if not, please do so as soon as possible.