Assuming you're referring to the Connect Nav+, you will need to remove it from the dashboard and remove the top cover. The grey part inside the top of the unit is the CD mechanism.
There's a lever on the top of the CD mechanism to mechanically eject a stuck CD. Unfortunately I can't remember which one it is but it should be obvious.
If you can't find it, I have some spare CN+s. I'll dismantle one to find out where the lever is for you.
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Picture credit: danhans115
I bought it used and it never worked.....