putting them in fields next to each other if you can, or introduce them with a fence inbetween first.  neutral territory is usually best with more dominant horses so if you can but them both in a different field that may make things easier.  just make sure they have loads of room if you are going to put them together.  horses generally bond faster if they only have each other too.

i really wouldn't put in any food because that gives them something to fight over.  let them establish a heirachy first.  keep an eye on them but keep out of the way and give them space.

the best you can do is leave them to it but keep an eye out.  horses rarely intentionally hurt each other, some can look very aggressive but rarely be violent.  its usually all show anyway, and if you react it can often make the situation worse!

overall, the most important thing you can provide horses with is space.  but really it sounds like you'll have no problems just putting them together in a field and keeping an eye on them from a distance.  horses are very social and intelligent and always sort themselves out, especially if they are lonely.

good luck Xx

Put them in adjoining paddocks for a week or so. Then put a few piles of hay in a big field and turn them out together and see what happens. You could try introducing them on a lunge line or leadrope, but if things turn nasty you could get in the way. I'd just let them be alongside then turn them out, they'll sort things out for themselves, I doubt if she's old and he's poorly that they'll go too mad and hurtle about or anything!