From I-70, west of Idaho Springs, take exit 238 for the Fall River Road/CR 275. This paved county road 275 ends in the vicinity of a mountain village called "Alice," mostly a collection of summer cabins, etc. This is the same road that leads up to the well-known St. Mary's Lake and Glacier. The road follows the Fall River in a generally NW direction. After over six miles miles, the road makes a second, abrupt switchback to leave the Fall River drainage and climb up to St. Mary's Lake and Alice. Continue north into Alice. Watch for a parking lot on the left side of the road just after the trail/old roadbed heads up to St. Mary's Lake and Glacier. This smaller lot will be just a short distance past another, larger parking lot for the defunct "Eclipse Snow Park." Coordinates above are for the smaller parking lot. The lot is directly west from Quivira Lake. If you come to the end of the pavement and Silver Lake, you've gone past the trailhead and parking lot.
This entire area of Alice is private property. For at-large, primitive camping, you're better off driving back on one of the Forest Service roads such as FS 701.1 up to Fall River Reservoir. If you don't mind packing in some gear, you could head up to St. Mary's Lake and set up a tent if camping is allowed there any longer. Check with the Forest Service.