I have a sick frizzle chick.. think it has the RSV stuff sleeping ALOt and sneezing...how much tylan can I give her? I'd say about 1 to 2 months old
Can you post some photos of your chick or a video of her? (for video, upload to youtube or a similar platform, then provide us a link).
Photos of her poop would be good too

Can you tell us how old she is?
Does she have other symptoms that accompany the lethargy and sneezing - does she have mucous, coughing, facial swelling, wheezing, eye discharge?
How
often is the sneezing?
How is she housed - in a brooder, in a coop/run, etc.?
Any mold/mildew in the area that she is kept?
How long have you had her, where did she come from, is she the only chick you have, do other chicks have similar symptoms?
There can be many causes of sneezing some of the most common are dust, mold, poor ventilation, use of disinfectants/sprays (irritants) and respiratory illness.
If you are dealing with a respiratory illness, an antibiotic like Tylan50 may help with secondary infection or if it's Mycoplasma. If it's viral like Infectious Bronchitis, the illness will have to run it's course. Injectable Tylan 50 is dosed by weight and has a wide range of 10-40mg/kg - this is given 2-3times a day.
The lethargy is very concerning. Chickens with respiratory illness can become lethargic, but you need to try to figure if the lethargy is from respiratory disease or if it could possibly be due to something like Coccidiosis. If you have a vet that can see her or that will accept a stool sample for testing, that would be best.
In the mean time, keep her hydrated and encourage her to eat.