Where is the Instagram account login, check like this:
First of all you have to open the Instagram app in your phone, after that you have to go to your profile, click on the current three dot/line on the corner on the right.

After that you are first seen to click on the account center (Accounts Center) option.

Now you will see the password and security option on scrolling downwards, which has to be clicked.

After that you have to click on Whare You’re Logged in.

Now you will see that on which device your account is login, from here you can log out from those devices one by one.

Here you can easily check that if your account is hacked, then where is the login.