Zoom in and/or pan around to examine the board.
(
Note that you now have a LRNUKE at Braxx.)

Purchase a SRNUKE at R1.

Strike Axia with the LRNUKE from Braxx.
Drag a SRNUKE from the item panel to R1.
Hold ALT (or use the RIGHT mouse button)
and drag the LRNUKE from Braxx to AXIA.
(
Use the arrow keys to pan while dragging.)