Fitting an image to the worksheet

You probably need to do some basic research (youtube, help files etc) on object handling and manipulation using the pick tool. Everything is there at your fingertips. Or alternately just mess around until you find out what does what.

Pick tool, shape tool and crop tool would be a good place to start learning

Just resize it, but uf the proportions of the image are not equal to the sheet you will need to adjust a little the picture - cut it. Or you can click twice on the rectangular tool and you will create a rectangular with A4 dimentions on the page. After that put the picture in it with power clip and click on Fill frame proportionally. Also look at the resolution of the picture after resizing and if it satisfyes your needs everithyng is OK.