How to make the Photo smaller inside every article, can click to enlarge

sorry, its hard for me to explain, cuz english is my second language,

for more understanding please check this website… https://www.rotikaya.com/kekasih-abadi-duet-pertama-yusry-kru-lisa-surihani/

as you can see, the photos inside the article become thumbnails, when I click any of the photo it’s become larger, but it’s “STILL INSIDE THE WEBSITE”

For an example: the original url is this https://www.rotikaya.com/kekasih-abadi-duet-pertama-yusry-kru-lisa-surihani/

when I click any of the photo it’s become like this :
https://www.rotikaya.com/kekasih-abadi-duet-pertama-yusry-kru-lisa-surihani/11-kekasih-abadi-duet-pertama-yusry-kru-lisa-surihani-rotikaya/

so I want to know what plugins I need to use… please share to me ASAP