Someone help me out idk what to do DHS and my son?

here recently i have been getting alot of people telling my that my ex is seriously neglecting my son there saying that she only feeds my year old son 1 can of formula a week that whenever he crys in his room she just leaves him in there to cry and dosnt do anything she constantly has him eather in her arms or in a car seat she almost never changes his diper unless its litteraly overflowing with pee or crap and she constantly leaves him with people every single day almost just so she can go hang out with her friends she is 19 and she dosnt knw what she is doing or dosnt care so i want to go to dhs so they can do something about it how exacly would i go and do this do i just go in there and tell someone that she is neglecting my son and someone needs to go and check on things or what exacly?