Hello Ravi, and welcome to the forum.
Please note that while Sparx staff are pretty active on the forum, most of us are regular users. So this is not an official support channel (those are available in the Support menu up top), although I'd say for usage questions like this one it's probably the better option. There are more of us than there are of them.
Strictly speaking, element creation from toolbox is not drag-and-drop but select-and-place. You click the element type (and release the mouse button), move the pointer into the diagram and click again to place the element. Between the two clicks, the element type is highlighted in the toolbox and the pointer switches to the create-element shape (while in a diagram).
Creating a connector from the toolbox starts with the same select-and-place in that you select the connector type (which is highlighted), then click the source element, but you then drag to the target element.
If you omit the drag and just click one element while in connector creation mode, you get a connector whose source and target are the same element.
If you drag to an empty area of the diagram and release, you are presented with a menu of element types. Selecting one of these causes EA to create the connector and for its target a new element of the selected type.
If you drop the connector on the wrong element, you can move a connector end (either one) by selecting the connector, moving the pointer to the spot where the connector meets the element (the pointer changes to an up-right arrow), and then click-and-dragging to the correct element.
HTH,
/Uffe
