Instagram doesn’t want you spamming your bio with links, so it only allows you to add one.
But with only one link, you have to make the difficult decision of what content you want to promote. (It’s like picking your favorite child, but harder.)
Your profile can contain multiple links (YouTube videos, an online store, your blog, etc.), links to your messengers (FB Messenger, Skype, WhatsApp), and links to your other social networks.