The 25-year-old, who been training with the club for the past month, has previously played in the United States for West Texas A&M University before a spell in Iceland last year.
Everson, who will be able to feature against Aldershot on Saturday if the clearance comes through, scored seven times in 10 games for Tindastoll before being part of the Premier League side Breidablik who qualified for Europe.
"Ben is someone I've had for three or four weeks now and he's done extremely well," manager Gary Mills told the club's official website.
"I've liked what I've seen so I've given him a contract until the end of the season.
"I have signed him for the right reasons because he looks a very good player".