you undo the clamp from inside the enginebay
remove the carpet from the pedals
push the old bush out
put the new bush in
job done

unless there is something else about the column that needs doing? if the inner shaft moves up then it just means it's not going to reach the bit at the bottom, othewise it's not going to move?

also, the colapsable bits of the column do tend to collapse after a few years so it's also worth just removing the steering shroud to see if this is the case, it's covered by some sticky foam so don't pull that off if you can help it, you should be able to feel the corugated section of tube to see if it's tight up aginst itself or ridged like it should be