Water it thoroughly, remove any fallen or dying leaves and keep it in a shady area while it rehydrates and recovers from its traumatic travels in a pitch black box.
Also as you mentioned there seem to be spidermites, be sure to hose the leaves off gently, hitting both upper and lower faces. Doing so will help discourage the spidermites.
When you notice new leaves emerging you can gradually start to lightly water your tree. Just don't keep it real wet. You can increase watering once it has made new leaves. Once it seems to have recovered you can gradually move it into brighter light and eventually into more sun. Just don't do that too quickly so as to give the tree time to acclimate to the extra light.
Just as a matter of curiosity which red cultivar did you buy?
Cheers!
Paul M.
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