If the comb is nearly black in color, it's what beekeepers call "brood comb" and it's not going to yield a lot of beeswax. The wax rendered from brood comb will range from dark gold to brown in color. Beeswax from actual honey comb will be pale yellow to light gold in color. You will also get a better yield of wax out of honey comb. The beeswax you buy from commercial sources is often bleached to a near-white color, so don't expect that from the wax you'll get from your friend's comb.
I do the first rendering of comb in a solar melter. Solar melters are not hard to make, but probably more work than it's worth if you're only going to render comb just this once. For your situation, I'd suggest doing all of the rendering in a hot water bath (bain marie). Find a large dutch oven or stock pot -- preferably one that you won't be heartbroken if it is permanently stained from the comb. It can be cleaned for food use again, but it might never look the same.
Put 2-3 inches of water in the pot and bring to a simmer. Break up some of the comb and put the chunks in the water. Don't heap the comb high in the pot, because you need to be able to stir and push the comb into the simmering liquid as you go. Too much dry comb in one big pile makes stirring harder.
I use a chopstick for stirring since it's disposable, but you can use a metal utensil if you don't mind cleaning off the beeswax later. Keep adding comb to the pot until the pot is 1/2 to 2/3 full of melted stuff. This will be a mixture of melted wax floating on top and the water and comb that won't melt on the bottom. It will look ugly.
Turn off the heat and let the mess sit quietly at room temperature, so the wax can separate as much as possible from all the rest. When the wax has solidified, remove it from the underlying water and bits of comb. If you can get it out in one piece, that's great, but I usually have to break it up into large-ish chunks to get it out of the pot. (Tip -- Water usually spurts up when you make the first crack in the solidified wax, so you might want to work outside and keep your face away from the pot. I learned this lesson the hard way.)
Discard the water outdoors in an out of the way spot -- don't put it down a sink drain. Remove the loose debris on the bottom side of the wax by scraping with a knife or spatula. If you have another batch of raw comb to render, recycle those bits into the next batch. Otherwise, discard the bits in the trash or outdoors.
Now that you've got the first rendering done to remove the worst of the debris, repeat the rendering step at least one more time to further clean the wax and remove as many of the fine particles as possible. With clean honey comb, I normally do just two renderings. Dark brood comb will take 3 or even 4 renderings.
You can store the rendered wax chunks as-is or you can gently remelt them and pour the wax into a plastic tub with tapered sides. The tapered sides will let you pop the solidified wax out in one piece.
If I have some really nice wax that I want to use for salves, lip balms, etc., I will line a cookie sheet with parchment paper or aluminum foil. Melt the wax and pour it in a thin layer over the paper/foil and let the wax harden. Peel the wax off the paper/foil, break it into bits the size of a quarter or smaller, and store them in a plastic bag. These small, thin pieces of wax are easy to weigh and melt. Thin sheets of wax can also be set out in the sun to bleach if you want to lighten the color somewhat.
To clean your equipment, heat the pot and metal utensils on the stove or with a heat gun until the wax residues just melt. Wipe with paper towels or wadded newspaper to remove the melted wax. Repeat until most of the wax residue is gone. Wash in hot soapy water.
Hope this helps.
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