OP, your DH will need to have his leg elevated when sitting, with the ankle higher than the knee (lymph nodes at the back of the knee are where lymph fluids causing the swelling will be absorbed - gravity needed to get it from lower lwg to the knee). BUT, he will also have to mobilise several times a day to reduce his risk of DVT.
The hospital will have told him whether he can weight bear on that leg or not, either full, partial, toe-touch or not at all. Nailing can usually weight bear to some extent as pain allows. He might well find it easier to move around the house if he has elbow crutches rather than a frame - especially if you have stairs. Crutches allows him to share his body weight between the sound leg and his arms - most men have better upper body strength than women, so find this easier. Crutches should always be placed in front of the feet/foot, so that they form a triangle/rectangle. To walk, crutches forward, then the nailed leg to just behind the crutches, weight pushed down through the hands, bring the sound leg up to meet the nailed leg. Minimises the weight on the nailed leg at all points in the cycle. He would be able to stand at the kitchen worktop to say, make himself a cup of tea (weight on sound leg, toe-touching nailed leg for balance), but he would need someone else to carry the tea back to where he is sitting (both hands occupied with crutches).
Stairs - hold onto handrail, crutch in other hand. Take weight on crutch/handrail, sound leg up first, then nailed, then crutch. The reverse for going downstairs - crutch first, slide hand down handrail to same level, nailed leg down, take weight on arms, sound leg down.
A cross-body bag will be really useful to carry eg newspaper, pen, phone etc. Do not let him use a bag in one hand, it can start swinging and pull the crutch out from under him.
He'll find his triceps get stronger after a few days so it will get easier every day and less tiring on his arms.
If he's non-weight bearing or toe-touch, one possible problem is the ankle - the foot will fall into a toes-pointed position, which can lead to the calf-muscles shortening and it then being uncomfortable to get the foot flat on the floor. If you can prop the foot into 90 degrees in some way whilst the leg is elevated so much the better, otherwise be aware the muscles will need to be stretched out later - not difficult, can be done over a few days.
He will need to use chairs with arms, preferably quite high chairs - it's very difficult to get up off a low chair with or without arms when you can only put weight through one leg. Safest way - elbow crutches in one hand in an H shape (both handgrips together, in one hand), other hand on the arm of the chair. Get bottom to the edge of the chair, sound leg tucked under you with foot flat on the floor, nailed leg straight out in front taking no weight. Rock upper body forward, push through both arms into standing position, toe-touching only on nailed leg. Bring crutches to front, free hand through the arm cuff and taking both handgrips, thus freeing second hand to go through the other arm cuff. separate crutches and position in front of you.
Do encourage him to move about as much as pain allows. Muscles deteriorate rapidly if not used.