Thank you for reaching out to us. By default, you'll draw tiles which are on the first (0) layer. This is why you keep selecting the floor tile in your report. If you wish to select other layers, make sure to uncheck the "Lock Z-position" checkbox in the default brush settings, and increase the Palette Z Position. Keying in number 2 in the Palette Z position should select the wall tiles in your tilemap.
Do let us know if you have any further questions!