You can apply for your Employment Pass (EP) as soon as the company has been incorporated and the EPOL account has been set up (usually 7 -10 working days from date of incorporation).
Suggested Readings
Can I apply for an Employment Pass prior to incorporating my Singapore company? Why do I need to appoint a resident director?
How many paid annual leave days are employees entitled to?
Can I apply for Permanent Residence if I am on an Employment Pass?
Can I bring in my dependants on an Employment Pass (EP)?