If your uncle is a Canadian citizen and resides in Canada, you do not have to do anything special. You just buy a Hunter Host license and have him added to to the license. He must then purchase his Non-Resident canadian tags and you are free to take him hunting. If he were a Non-Resident Alien, there are forms that are required to be filled out. See the following from the Regs:

A Hunter Host

Must be an adult resident, and be eligible to hold recreational hunting licences.
Must be the holder of a valid Hunter Host Licence (below).
may not provide services for gain or reward, or accept remuneration, directly or indirectly, for such services.
may host a maximum of two (2) hunters/year, either Non-residents (Canadian), Non-resident Aliens or a combination thereof. If hosting 2 Non-resident Aliens, at least 1 must be a relative.
may host Non-resident Aliens only if the host has not hosted a Non-resident Alien in the previous two (2) fiscal years (April 1 to March 31).
must report to the Fish and Wildlife Division by December 31 in the year of harvest, all hunting activities by the Non-resident Aliens he or she hosted.
must accompany the hunter(s) named on his or her Hunter Host Licence while they are hunting big game under the authority of the Hunter Host Licence.
Hunter Host Licence
A resident who wishes to be a Hunter Host may purchase a Hunter Host Licence at any private licence issuer. You must have the WIN(s) of the non-resident(s) at the time of purchase. You must ensure that the hunters you host are named on your Hunter Host Licence. If you purchase your Hunter Host licence naming one hunter and you decide to add a second hunter to your licence at a later date, you can do so at no additional charge. Return to a private licence issuer with your licence and have it amended. Once you have purchased your Hunter Host Licence, the hunters may purchase their licences.

A Hunter Host who plans to take a non-resident alien hunting must do the following:

Go to a Fish and Wildlife Division office and initiate an application (including statutory declaration). Sign it and have your signature sworn. If your Non-resident Alien is not a relative, you must start this process by August 31 or February 28 as described above.
Have the Non-resident Alien sign the application and have his or her signature sworn. (If the Non-resident Alien does not have a WIN, have him or her fill out a WIN application at the same time.)
Take the completed application to a Fish and Wildlife Division office. The application will be reviewed for final approval and keyed into the automated licensing system.
When you are notified that your application is approved, go to any private licence issuer and purchase your Hunter Host Licence (see above) and the appropriate Wildlife Certificate and licences.