you can get trial Rebex.Ftp.dll and dependency dll's at Ftp/Ssl download page. Or, you can buy these dll's at Ftp/Ssl purchase page. Or, if you already download one of above or one of our sample from Ftp/Ssl samples page, provide as more info please, such as if your app is running on CF (I presume that based on you run it on a device), if it is our sample and which or it is your app.
Also please make sure you are referencing other libraries the "Rebex.Ftp.dll" depends on. When using Rebex.Ftp, you have to reference the following DLLs: