1 - Top right corner . Click on edit pipeline 

2 - On the next screen again on top right corner click the 3 vertical dots to find Switch to code version (YAML) 

3 - Edit this yaml file . 

If you want to import all the tables from a specific sql server schema use objects as schema . example .

If you want to import specific tables use objects as table . example below . you can edit this yaml to add the tables manually or using a script .