Add Instagram export .html files (reposts.html, saved_posts.html, post_comments_1.html, liked_posts.html, following.html) one at a time. Files are parsed entirely in your browser and never uploaded as-is - only the extracted rows are ever saved.
Click Start, log into Instagram in the tab that opens (that's a live view of a browser running on Cloudflare, not your machine), then come back and click Finish.
Or, manually: open DevTools → Application (Chrome) or Storage (Firefox) → Cookies → https://www.instagram.com, copy the "sessionid" cookie value, and paste it below.