Follow the 4 steps to view your 18+ content on Instagram:
(1) Go to your profile in the bottom right to go to your profile
(2) Tap the Settings menu in the upper right corner.
(3) Tap Suggested content, then tap Sensitive content.
(4) Here you can decide whether to keep the setting at its default state (“Standard”) or to see more (“More”) or less of some types of sensitive content (“Less”). You can change your selection at any time.