I can see this for an advanced question but for a simple one the information is there. It's also nice to see folks at least try to find their answer before coming and posting...but in the case of the OP I do not see any of that.

For starters if the OP would have looked at their ticket they would have seen that neither of their flights go in or out of Terminal A. But should a mistake have been made and the OP thought LAS or CHS operated out of A and wanted to find the transit time between the two EWR terminals a simple search of "EWR Connecting Terminal" yielded this thread: Connecting Terminal C to A at EWR. This directly answers the OP's question of "getting from terminal C from an express jet to terminal A". But should that thread have lacked the exact information the OP needed, posting a follow up question on that thread vis-à-vis starting a new, poorly-titled one would have allowed the group to contribute to the already existing discussion so when another person had the same question down the road all they would need to do is find that thread and not look all over FT for scattered bits of information.

Please do not read this as discouragement for folks posting as there’s a plethora of unanswered questions out there warranting new threads. However, in this case the subject had come up before – and had been answered before – thus the creation of another thread was, IMHO, redundant.