You can publish your Sketch artboards directly to Axure Cloud with the Axure Cloud desktop app.
Launch the app and install the Axure plugin for Sketch when prompted.
In Sketch, select the artboards you want to publish to Axure Cloud.
In the top menu, go to Plugins → Axure → Export Selection to Axure Cloud. You'll be taken back to the Axure Cloud app.
In the Axure Cloud app, select the workspace and artboard project you want to publish your Sketch assets to.
Alternatively, select Create New Project in the Project dropdown to set up a new artboard project.
Click Upload to publish your Sketch assets.
Once the upload is complete, you'll be taken to the project's Overview screen, where you'll see a thumbnail for each artboard.