Thank you for reaching out to the Samsung community! We would like to inform you that the option of "install app from unknown sources" is available under settings>>apps>>3 dot>>special access>>Install unknown apps>>Enable the applications from which you want to download and install the apps.
Be sure to hit ♡ when you find an answer that works for you. For Further assistance, you can get in touch with us via Live Chat option by following- http://livechat.support.samsung.com/Customer_new/IN. You can also connect us via Samsung Members web community by following mentioned url-https://community.samsungmembers.com/en_IN#/
