In the Lightroom Photoshop App:

Screen shot of Lightroom Photoshop app export
screen shot of settings for image export in Lightroom Photoshop App


With the image selected, choose the download icon. From the bottom of that menu, select Export As …

From the Export As menu, select jpg, long side 1024, and image quality 50%.

In Lightroom Classic:

Select File>Export.

Setting to create smaller JPGS in Lightroom