From Tsim Sha Tsui, please take the HK metro of Tsuen Wan Line and get off at Admiralty Station. Out of the exit B, you could catch the bus 629 to the Ocean Park directly.
As for visiting the peak, firstly you have to return to Admiralty by 629. Then, you could walk to the Lower Peak Tram Terminus in 20 minutes or take bus 12A there. The second method, take the metro to the next station-Central, out of the Exit K and then transfer to the bus 15C which could take you to the Tram Terminus at Garden Road directly.
Please note, at every Sunday and national holidays, the bus 315 shuttles between the Ocean Park and the Peak.

From the Peak to Tsim Sha Tsui, you could return to Central and then take metro back. Or, you could take the 15C at the Tram Termius to Central Pier, where you could take the time-honored Star Ferry to back to Tsim Sha Tsui.