You can wait to report the employment up to 10 days from the actual start date. For
example, you start employment on May 1st; you will have until May 10th to report.
If you are approaching the 10th day and still have not received the portal link, you
can submit the employment form without first entering the employment in the portal. In the employment form 4th questions,
you will choose the option - "No because I do not have an SEVP account due to my OPT not being approved yet or
No, I have not received the SEVP portal link from USCIS.  The IPS DSO will receive
the form and enter all employment information within the SEVP portal. You will still
need to activate the portal once you receive the link for future employment updates
in the future.