Hi,
I suppose you were trying to use JA Extensions Manager. If so, there 2 steps you need to complete before been able to use the Manager.
1- Go to the Extensions Manager and click on Services Manager. From there, you can “Edit” the Joomlart Updates by entering you username and secret work, and save it. Then make it the default by clicking on the radio button and pressing on “Default” at the top right side.
2- After completing step 1, then click on “Configurations” located on the left menu, second to last. Without changing anything, just click on save. These should be the configs:
Local repository path: jaextmanager_data
Mysql path: mysql
Mysql dump path: mysqldump
After these 2 steps, then try again and see the magic.
Good luck!