He joins his new team-mates on a training camp near Leicester during the forthcoming week.
Youga, who has had loan spells at Bristol City and Bradford, is capable of playing on either side of the backline.
"Left-back is his usual position but he had a spell on loan at Bradford City last season during which he played against us on the right hand side" boss Nigel Adkins told the Scunthorpe Telegraph.
"I am delighted to have him with us. He is a player we have had conversations about since the beginning of the summer."