You can do it now - they're pretty hardy, but firm the soil down once you've done it to prevent wind rock.

Bamboo is right regarding planting out now ; my only issue is if the plant is acclimatised to the 'great outdoors' .
If nursery raised , it has most likely spent a lot of time in a polytunnel or greenhouse . Sudden exposure to cold winds and frost might not be exactly amenable to good health .

Adaptation would need to be rapid (not knowing the kind of Winter to expect) . If mine I would be inclined to wait until the Spring . Keep it fairly sheltered until then ; at least with a full growing season it would have time to get used to fluctuating day length and temperatures as they gradually rise heading into Summer .

Depends where it was when you bought it as to whether it needs hardening off or not - under cover but outdoors, harden off, standing out in the open, plant it now. Unless, that is, you've kept it indoors or something since you bought it... but I'd still harden and plant out, the topgrowth's going dormant now anyway.