Your technique is correct. As Koz points out, I hope you’re using a 78 rpm stylus (needle). If not, stop what you’re doing a get one before you continue.
Playing 78s at 45 is something that a lot of people do, since finding a quality 78 rpm turntable is difficult, to say the least. Since you are playing the disk slower than normal, tracking should not be an issue. The top frequency on a 78 will be around 8 kHz, and playing it slower will lower that to about 4.6 kHz.
You should reverse the RIAA equalization before changing speed - now the transfer is “flat”. Then change the speed. Then apply the “proper” 78 rpm equalization (whatever that may be - who knows if they are radio transcriptions!).
See this topic for more details on installing a reverse-RIAA curve into Audacity 1.3.x https://forum.audacityteam.org/t/reverse-riaa-curve/11026/1
Brian Davies suggests a different method for capturing 78s at 45, and has a free “Equalization” program that that simultaneously applies the proper reverse-RIAA curve (corrected for the different playback speed) and a chosen 78 rpm EQ curve. http://www.clickrepair.net/
– Bill