Please check for fire restrictions before you go: https://www.fs.usda.gov/detail/stnf/alerts-notices/?cid=stelprdb5392380.
Campfire permits are required to have a campfire or stove at a dispersed site. Campfire permits are available online at www.readyforwildfire.org/permits/campfire-permit/
Camping is not limited to developed camping. Almost all of the forest is open to those who prefer the quiet solitude of a completely undeveloped setting.
Generally, dispersed camping is allowed outside of developed sites within the forest unless otherwise posted. One exception to this is Lewiston Lake. Camping is prohibited within 1/4 mile of the high water mark with no exceptions. Other exceptions are the Mt. Shasta plantations area and McCloud River Loop.
Please call ahead to offices for current fire restriction and road information. Potable water, toilets, and other amenities are not available. Be sure to bring adequate water or be prepared to purify natural water sources before drinking. Camp at least 200 feet from springs, water, meadows, trails and roads. Camp at least a quarter-mile from designated campgrounds, picnic areas, trailheads, private property and state highways. If you brought it in with you, then remember to take it out when you leave (Pack It In/Pack It Out).
More details here: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fseprd771279.pdf