Both sterling silver and silver plated jewellery can tarnish. Sterling silver will tarnish slower than silver plated, however to ensure a long life for your items I would advise the following -

When you are not wearing your jewellery keep them in an air tight container, be it a jewellery box or the bag/box it is delivered in. Exposure to air can tarnish your jewellery over time.

Avoid contact with hairspray, perfume, creams and other aerosol products. If these come into contact with your jewellery it can increase the chances of them tarnishing.

Overall, enjoy your jewellery! It is made to be worn and enjoyed. Keep it safe but also don't keep it locked away in a box only to be looked at.