Hi,
To add a Layer Package to ArcMap you just need to double click the .LPK file. To give you a little more info on this - there's an application called the ArcGISFileHandler.exe which is associated with the various ArcGIS-related file types (e.g. .LPK) and this small application will determine what ArcGIS application to open... Regarding data packaging - to package ArcSDE based data you will need the data expansion pack.