Check to be sure the tenon is a good fit. Take your time here. It will make a difference to the like of the lamp and a firm fit makes the assembly and gluing easier.
Intermediate Woodturning Project
Table Lamp - page 5
connecting base to shaft and getting ready to wire.
Drill a 1/2" hole in the center of the base to intersect with the wire hole from the side.
I stopped the hole before it came out the bottom but there is no particular reason to do so and it may be easier to wire the lamp if the hole is completely through.
I like to widen the hole through the shaft to 3/8" for easier wiring and assembly.
Run the wire through the base and shaft.
Glue the tenon in the mortice with yellow glue or adhesive of your choice.