To register company online you need to follow these steps:
Before registering a company online you need to get ACRA’s approval for your company name;
Prepare all necessary documents (Particulars of shareholders/directors/company secretary, description on business activities and so on);
To register a company online, you can visit BizFile+ portal (maintained by ACRA).
There are a lot of incorporation service providers in Singapore. Incorporate Business Online listing will help you to choose the company that fits you best.