Thanks for contacting Microsoft Q&A platform.
It seems you are trying to upload a file from onprem and doing some transformations and storing the data to Lakehouse.
Please follow below steps to achieve your goal.
- Create a fabric workspace and select data source from where you want load data.
- Load data and make transformations as your requirement.
- Then click on data destination as shown in below screenshot.
- Click next on the next slide.
- select your workspace in the next slide it will display all your lake houses there and select your lake house.
Hope this helps.