If you can run an Ethernet cable, you can add an access point out there. While that is the preferred approach, if you cannot run a wire, you can use directional antennae at one or both ends and a wireless repeater out there.
thanks so for internet i run an ethernet cable from my wireless modem to the barn and add an additional wireless router? Is there a special ethernet cable for underground and i should mention this is northern michigan where it can get as cold as 20 - to 30 degrees below zero at times
or you can buy a spool of outdoor CAT5e, which is cheaper per foot and then crimp on the connectors. Best to use a crimping tool, so add that into the cost comparison.
The temperature won't be a problem for the cable.
Out in the barn you can either put a switch, or if you also want wireless there just use another router and turn off the DHCP so it will act as an access point with a 4 port switch for wired connections. If you go that route you will want to assign the access point an IP address on your main router that is either a reserved dynamic address (see address reservation in your manual) or a static address outside the DHCP server assignment range but in the network range, use the same SSID, wireless security type, and password on the access point as on the main router. Then your main router will continue to control all DHCP address assignment. For example, if your main router has a gateway address of 192.168.1.1, allow DHCP assignment of 192.168.1.2 to .127 and assign the access point an address of 192.168.1.128. Allow all of your devices to obtain an address automatically from the main router and you are good to go.