When you say barrel, is that the vessel you fermented the stout in? If so, you'll need to bottle it when it has finished fermenting. 10 days may not be enough for a kit to finish, sometimes it takes longer.
Is your barrel like one of these?
View attachment 27060View attachment 27061
If so, that's what we call a fermenter, or fermenting vessel (FV).
A pressure barrel (PB) is like this:
View attachment 27062
These are usually used for storing, rather than fermenting beer in.
If you leave your stout in the fermenter it won't hold pressure so you'll have flat beer, plus it will be sitting on all the dead yeast which can affect the flavour after a while.
Stout is good served from bottles or a pressure barrel, but you'll get more of a 'pub pint' head from the pressure barrel. I find 80-100g of sugar is about right to add to a pressure barrel if you aren't bottling. Some people don't get on well with pressure barrels as they can split or have trouble with seals, others use them all the time without any trouble.
I emptied my sole remaining plastic PB on Wed night. I already have a beer in the FV which was going into it. There are two 25-50mm cracks inside the shell at the bottom moving away from the seam which have now got bigger, so I can't trust it. The beer in the FV will now go into bottles and a recycled easykeg/minikeg I am trying out. The PB will get recycled since its made of HDPE, which, in my view is all they are good for.I was thinking of you when I wrote that. I guessed your PB radar may be switched on today!