Originally Yoshida trail starts from a shrine, that is - Kitaguchi Hongu Fuji Sengen Shrine in Fujiyoshida city, and a sign pointing to the trail can be found in the precincts. At 850 meters in elevation, it takes about 11/6 hours to go up/down the trail respectively.
If this sounds too daunting, there is a shortcut. By starting from Fuji Subaru Line 5th Station at 2305 meters instead, it can be cut down to about 6.5/3.5 hours.