If you want to repost someone’s content, you can use a free app called Repost for Instagram.
To repost on Instagram using the app, follow the instructions:
Step 1: Chose the post you want to repost and tap on the post options;
Step 2: Copy link;
Step 3: Open Repost for Instagram;
Step 4: You will see the post In your list;
Step 5: Select this post and choose the repost tag style;
Step 6: Hit Repost to launch your Instagram app;
Step 7: Chose if you want to repost to your story or feed;
Step 8: Publish your Repost.