Why do I get a wheels up alarm when I take off and put up the gear I missing something 

A lot of GA aeroplanes will sound a warning if you have the wheels up with the flaps fully deployed, or if you chop the throttle with the gear down, and some will give you a warning if you are below a certain altitude with the wheels up. Dunno if your aeroplane specifically features that, but I'd guess so.

If you want a good laugh, watch this video, two pilots, both apparently with several thousand hours, and they completely ignore the wheels up warning and ruin a perfectly good TB-20. Granted they have headsets on, but even so you can hardly miss that warning sound with the engine throttled back:

 

5 hours ago, AceFAB said:

Why do I get a wheels up alarm when I take off and put up the gear I missing something 

Haven't installed the Phenom 300 anymore but I remember that this was a very annoying bug in the release version.

This warning shouldn't come on at high power settings, e.g. after takeoff. 

IRL with Flaps up, 1 and 2 this warning should only come on at a low power setting and if below 700ft RA and below 160kts.