Water it well the day before and on the day. Cut off any finished spikes and trim dead or yellowing leaves. Prepare a hole a bit bigger and deeper than the one it wad in, put some compost and general fertiliser at bottom, then lift your lupin and transplant it in the new hole, settling it in and filling the hole to same level on the plant as before. Water well and regularly for a while and it should be fine. It will die back naturally and come up again next year.

Its better to wait until the autumn if you can though.