Apart from purchasing newly-issued bonds from the issuer(investment-bank), you can also purchase bonds that exist in the secondary market. This is known as purchasing bonds from the secondary market. The price that you required to pay would be the accrued(total) interest on the bond as well as its market value.
"A" buys a bond in the primary market with a face value of RM1,000 and a coupon of 6%. After 120 days, "A" sells the bond to "B" at the market price of RM950.
"B" would have to pay:
Market value of bond + accrued interest of bond over 90 days
= RM950 + (RM1,000 x 6% x 120/365)
= RM950 + RM19.73
= RM969.73 is the amount "B" pays "A" when he purchases the bond from the secondary market