You can't you find Sharpen AI as a plugin in Lightroom? Let's do the following:
1. Open Lightroom and go to Preferences:
For Windows: For Mac:
2. Go to the External Editing tab:
3. About halfway down you will see the Additional External Editor Section. If Sharpen AI is in the Preset list, delete the preset of Sharpen AI from there. If it's not, go directly to step 4.
4. Search or navigate to the Topaz Sharpen AI app icon. Select the program itself, not the whole folder. It will have an icon similar to the one below:
5. Name your External Editor with Sharpen AI:
Once the plugin is correctly set up in Lightroom, you can review: How to use Topaz Labs as a plugin to Adobe Lightroom Classic.