He enlisted in (old) Co. I at Clarendon, Arkansas, on June 20, 1862, for three years or the war. He was detailed on detached duty as a mechanic (see remarks below) in the Quartermaster Department at Little Rock, Arkansas, on July 15, 1862. During the general reorganization of the Trans-Mississippi Army on December 16, 1862, (old) Co. I was redesignated as (new) Co. C, and Private Collins and his comrades are filed under this company at the National Archives. The company was recruited in Monroe County, Arkansas.
Private Collins was still on detached duty at Little Rock during and after the reorganization, and never returned to duty with his regiment. He was still on duty at Little Rock when the city fell in September 1863. He was captured, but I've been unable to find a prisoner of war record for him. He may have been paroled in the field rather than sent to a prisoner of war camp.
His record states that he was detailed as a "mechanic" -- in the usage of the time, this could mean anything from a carpenter to a blacksmith. In Private Collins' case, he was apparently detailed as a carpenter.
The "J. W. Peay" you mentioned is Maj. John Coleman Peay, quartermaster of the Post of Little Rock.
"S. S. Anderson" is Col. Samuel Smith Anderson, adjutant-general of the Trans-Mississippi Department.