The short answer
HighLevel has no Kartra importer. You export leads from Kartra as a CSV and import them as contacts, download course videos and PDFs and rebuild the courses in HighLevel Memberships, and recreate offers, calendars, automations, pages and funnels by hand. HighLevel's Kartra migration guide lists what to move and in what order.
Leads to contacts
In Kartra, the guide says to open Communications, then Leads, tick the leads you want and choose Export from the dropdown, checking that email, phone, custom fields, tags and lists are in the file. Prepare it the way HighLevel expects: dates as YYYY-MM-DD, UTF-8 encoding, and no line breaks, emojis or empty columns. Create matching custom fields in HighLevel first, then import through Contacts and map each column. HighLevel has no Kartra-style lists, so turn list membership into tags (one tag per list works) and build Smart Lists from those tags once the import is done.
Courses and memberships
Kartra memberships have no importer, so budget the most time here. Download every video lesson and document from Kartra's membership area and back them up, and write down any quizzes or surveys, since those are rebuilt by hand. Group the files by module before uploading and check the formats (MP4 for video, PDF for documents). HighLevel suggests doing course work outside busy hours so current members are not disrupted. Once files are in HighLevel's Media Storage, the Import from Media Storage button inside a lesson attaches the same video or audio to several lessons without a second upload.
Offers, calendars, automations and pages
List every Kartra offer with its price and payment gateway, create matching products and offers in HighLevel, and grant access to the right contacts. Calendars are recreated in the sub-account's calendar settings with the same reminders, assigned users and meeting locations, Google or Outlook calendars are connected under Connections, and recurring events need their recurrence rules set again. Automations are rebuilt as HighLevel workflows. Sales, landing and checkout pages are rebuilt in the website builder, and funnels under Sites, Funnels, with opt-in forms wired to the new workflows. Keep Kartra live until a test lead has passed through every step.
More answers in HighLevel questions. For costs, see GoHighLevel pricing or run the cost calculator.