For Twitter:

• You may tweet links to your Instagram images from within the Instagram app, forcing your Twitter followers to click over to Instagram in order to see your photos. To begin, go to your profile and tap the menu button in the upper-right corner. Go to Account > Settings.
• You can sign in to your Twitter account by going to Linked Accounts > Twitter.
  Turning on the Twitter button before posting allows you to tweet photographs while uploading them to Instagram.
  
  For Other Social Media:
  
  
• You'll need to link your Instagram and other social media accounts in order to share photos.
• Tap your profile symbol on the Instagram home page, then the menu in the top right.
• Select 'Account' > 'Linked Accounts' from the drop-down menu.
• Enter your login details for the account you want to link. A variety of social media sites, such as Facebook, Twitter, and Tumblr, can be linked.
• You can now make it such that when your photo is shared on Instagram, it is also shared on other social media accounts:
• Select the + sign in the center of the bottom of the screen in the Instagram app. Tap 'Next' after selecting the image you want to share.
• Apply whatever filters and edits to the photo that you wish. Tap 'Next' once more.
• You'll have the chance to write a caption, tag friends, and add a location on the final screen before the photo posts. You'll see a list of your Instagram profiles at the bottom of the screen (if you have several). A list of all the social media accounts you've linked to your Instagram account will also appear.
• Toggle on all of the social media sites where you wish to share the image.