The quick answer is you can not. Episodes beyond the previous season are not shown on Saturday or Sunday broadcasts of the syndicated Wheel of Fortune show. The Game Show Network (GSN) used to broadcast older episodes of Wheel of Fortune and may again in the future. Episodes of Wheel of Fortune have not been released on DVD and are not available for online viewing at any site except for clips from certain shows on Wheel of Fortune .com and similar sites.
I don't believe you will be able to find a copy of a 1989 Wheel of Fortune program unless you went directly to Wheel of Fortune.
Wheel of Fortune - 1975 1988-06-14 was released on: USA: 14 June 1988
Wheel of Fortune - 1983 - 6.29 was released on: USA: 13 October 1988
Wheel of Fortune - 1983 - 5.81 was released on: USA: 4 January 1988
Wheel of Fortune - 1983 - 5.83 was released on: USA: 6 January 1988
Wheel of Fortune - 1983 - 5.93 was released on: USA: 20 January 1988
Wheel of Fortune - 1975 1988-02-08 was released on: USA: 8 February 1988
Wheel of Fortune - 1975 1988-10-03 was released on: USA: 3 October 1988
Wheel of Fortune - 1975 1988-06-14 was released on: USA: 14 June 1988
Wheel of Fortune - 1983 - 6.29 was released on: USA: 13 October 1988
Wheel of Fortune - 1983 - 5.81 was released on: USA: 4 January 1988
Wheel of Fortune - 1983 - 5.83 was released on: USA: 6 January 1988
Wheel of Fortune - 1983 - 5.93 was released on: USA: 20 January 1988
Wheel of Fortune - 1983 - 6.42 was released on: USA: 1 November 1988
Wheel of Fortune - 1983 - 5.82 was released on: USA: 5 January 1988
Wheel of Fortune - 1983 - 5.84 was released on: USA: 7 January 1988
Wheel of Fortune - 1983 - 5.85 was released on: USA: 8 January 1988
Wheel of Fortune - 1983 - 5.86 was released on: USA: 11 January 1988