The Brackloon Wood trailhead is about 6 km (3.7 miles) south of Westport on the Leenane Road (N59). As you are headed south, turn right at the signpost for Owenwee, and the forest entrance is about 250m ahead on the right.
From the entrance to the forest, follow the purple arrows and enter through the wooden gate. Continue to follow the purple arrows along the track. This portion of the walk is also part of the Croagh Patrick Heritage Trail, which is marked with yellow arrows and the familiar walking man logo. After about 500m there is a y-junction with a wooden bench, where the loop portion of the walk begins. Continue straight (rather than left) along the path.
Continue downhill past a signposted forestry research site. At 300m from the 3-way junction, the path passes close to the Owenwee River on the right. After another 1,000m there is a wooden gate on the right. Here, the Croagh Patrick Heritage Trail exits through this gate onto a tarmac road with potential car traffic.
To continue on the Brackloon Nature Walk, do not exit the gate; rather, bear left along the loop to return to the forest entrance where you started. As before, follow the purple arrows.
The path goes uphill and then continues 1,000m downhill to return to the junction with the wooden bench. This completes the loop. Turn right and continue 500m back to the trail head.
The walk is 4km (2.5 miles) over a gentle grade.
A trail map is available here, along with some additional information.