Assuming that the Leightonhill east of Brechin is the right one, which does look likely, there is a photograph of it at
http://www.geograph.org.uk/photo/112069The forester's cottage may or may not have been or be among the farm buildings, or it may be or have been separate.
You can see the 1865 six-inch Ordnance Survey map of the area at
www.nls.uk and at
www.old-maps.co.uk. If using the latter, you can home in on Leightonhill by entering Coords 363300 761500 in the search boxes on the home page.
To find out where James Young worked, you would need to find out who his employer was. This isn't necessarily as difficult as it sounds, because the chances are that his cottage came with the job, so all you need to do is find out who owned the cottage.
This information is available in the Valuation Rolls. The late 19th century ones list every house, plus the names of the proprietor, tenant and occupier. The VRs are not available online, so you would need to get someone to have a look on your behalf. There are sets of VRs in the Angus Archives at Forfar and in both the National Archives of Scotland and National Library of Scotland in Edinburgh. To find Leightonhill you must know which parish/district it is in, because the VRs are arranged within parishes/districts.
You (or whoever looks on your behalf) need to find a VR which lists the forester's cottage with James Young as tenant or occupier. If he is the occupier, then the tenant will be his employer; if he is the tenant, then the proprietor will be his employer.
If he was employed by an estate, there may be estate records which mention him, or mention the forest plantations on the estate, and these may also be in the National Archives of Scotland.