You can do so at an ATM and Internet Banking (not available on Mobile Banking).

Via online banking

1. Go to https://www.ocbc.com/login.   
2. Under "Investment & trading", select "Initial public offering".

Via ATM

1. Select "More Services".

2. Select "Investment Services".

3. Select "Electronic Security Application".

4. Select the IPO you wish to apply for.

Unused CPF funds will be refunded to your CPF Investment Account, which are then transferred to your CPF Ordinary Account at the end of the month.

You can use cash to apply for any such issue at any OCBC ATM.

For the duration of the IPO, this service is available between 6:30am to 9:50pm on Mondays to Saturdays and 8:00am to 10:15pm on Sundays and Public Holidays.