The Republic of Ireland international praised his new head coach, having previously worked with him at Brighton, where he made his senior debut in 2021.
Ferguson is excited for the opportunity to develop further under Potter during his time in east London.
“It feels good. It's a very good feeling,” Ferguson told club media.
“Coming here and looking around the stadium, it just shows you a glimpse of (how big the Club is).
“The opportunity to come here was definitely high up on the list for me, and obviously, I knew the Head Coach (Graham Potter), so I knew it would be good to be working under him again.
“If you come in somewhere in January, you want to settle in quickly, and if you know people there, it'll make it that bit easier.
“Bruno is a good guy. He loves working one-on-one, so when you're working with him, he's all about the little details and if you're doing it right or not. Billy (Reid) is a good lad as well, and he brings it all together, so it'll be good to see everyone again.”