Zoom in or go closer with a wide ?
As a beginner, Its very important to understand the effect of focal length on the appearance of the subject you are shooting. In other words, focal length effects the perspective and thus distortion in a photograph. Long focal lengths show flattened perspective where as short focal lengths show exaggerated perspective, when used closer to the subject.
As you begin with photography and you mind is per occupied with apertures and shutter speed, do keep in mind that when you want to fill the frame with the subject, optically go closer instead of physically going closer. On the zoom lens that you have rotate it towards the longer focal length (bigger number) instead of towards the shorter focal length. Mover towards tele instead of moving towards wide. If you are at wide focal length, it would be better to step back and move towards Tele to get the same frame and composition. You will notice, your subject especially if you are shooting a portrait will start looking much more pleasing compared to the wide angle photograph with distorted features.
Wide angle and Distortion
Both the photographs above have been shot with 24mm lens just that one is closer and one is a bit far off. Since the camera is still not very close there is no apparent distortion as such.