You cannot add a clickable hyperlink directly in an Instagram post caption
Add the link in your bio and tell people to check the bio
Use Instagram Stories with the Link sticker
Add a link to your Instagram profile website field
Use Instagram Ads with a clickable call-to-action button
Put the URL in the caption as plain text
Use a shortened or easy-to-type link
Use Link in Bio tools to share multiple links
Add the link in a comment and pin it if needed
Use Instagram DM to send the link directly to followers