Warning: During the fall rut (mating season) for mountain goats, you may find this trail closed. From the picnic area parking on the west side of Echo Lake, walk south along the lake-shore path to the SW corner of the lake and keep going south to intersect Trail #52. Turn right and begin following the Chicago Lakes Trail #52. The trail more or less contours south for a half mile before reaching the first switchback that begins the series of switchbacks that drop the trail down to Chicago Creek. Elevation loss is about 280 feet. There are some places along this section where the drop-offs are quite steep. When you reach the creek, there's a hewed log bridge to aid in crossing. Cross on over and pick up the old roadbed that heads SSW to Idaho Springs reservoir at 10,617 ft. It's a half mile to the reservoir dam.
Beyond the reservoir, the old roadbed will turn to trail at the Mt. Evans Wilderness Boundary, well marked with signs & registration instructions. As you head into the wilderness, the trail takes you into an old forest fire burn from 1978. This area can have abundant wildflowers in the middle season. The trail will also leave the valley bottom and begin to gain quite a bit of elevation on the north side of the drainage to avoid the willow-clogged creek. As the trail approaches the first lake, it is still climbing through a lot of brush, then begins to make a descent. It is after the beginning of this descent that there will be a trail intersection, where the trail begins to head up again. The left fork will take you down to the lower lake. The right fork will continue to the upper lake.
To reach the upper lake, the trail passes through a steep section that may require some very minor scrambling. While the lower lake is about treeline in elevation, the upper lake at 11,760 ft. is above treeline. Nevertheless, there are still plenty of willows. This "approach" ends where the trail crosses the stream outlet for the upper lake. The upper lake is a very popular backpacking/camping destination. In fact this trail is part of the much longer, but still popular Mt. Evans route. The following link is to a pdf document by the forest service that covers all the trails in the Mt. Evans Wilderness including the Chicago Creek/lakes trail.: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprd3798847.pdf
See the Echo Lake trailhead information for camping beta at the Echo Lake campground. For wilderness camping at the upper Chicago Lake, the best opportunities appeared to be at the NE end of the lake in the vicinity of the outlet or on an elevated bench above the lake on its' SE side.