The process of a trade happens through December in Career mode, unfortunately there is no way to skip games so you will have to play up to that point. Check the Calendar date in the news section when you are driving/on the plane.
Around the beginning of December you will get a cut scene of you and your agent discussing trades, hes letting you know that the option to request one is coming up
Fast forward to around the 13th-15th and you'll be called into the GMs office and have the option to request a trade
After that he'll say I'll let you think it over for a few days, after a few more days he'll ask you if you are still sure, click yes and achievement unlocked.