This is the website of SSB. http://www.sgs.gov.sg/savingsbonds/Your-SSB/This-months-bond.aspx
Every month SSB will update with new tranche for purchase with appropriate rates as below picture.

Purchase is simple online. I have tested few times using DBS website. Application is $2 each time.
Dividends credited to my DBS saving account after 6 months automatically.

To sell is not hard too as I have tested it literally. However do note your transaction and amount each time you purchase or withdraw as there is no easy access to SSB historical records that you can tell in the website when you sell. Bank statements in the web is backdated to 2 months so provide no helps too. However I do get paper mail statement as equity trades done.

The highest effective interests rate is only if you hold it for 10 years and is quite attractive considering is “risk-less”. However if you …