You just have to make other trades in order to clear the space. Try trading to a team which has cap space (normally the Bobcats in the first year of a Dynasty).
The procedure's the same on all versions. You either need to make a trade with a team that has cap space (and thus can take higher salaries in return) or trade for players with expiring contracts, which will give you cap space at the end of the year if you have enough players' salaries coming off your books.