Please follow below mentioned steps to open adhoc interface with preselected metadata.
Step 1:Get the path and file name of the metadata you want to pass to adhoc report create, to get the path and file name follow below steps:
1. Click on the file browser

2. Open the metadata which you want to pass to report create.

3. Right click on the metadata to open the context menu and click on the properties

4. Now note down the the path and the file name of the metadata.

Here,
dir : 1463377807724\1463377836985\
File: e9be6771-995b-40eb-a01c-304857a100a1.metadata
Step 2:Passing the metadata file to adhoc report create url
Example: http://localhost:8085/hi-ee/adhoc/report-create.html?dir=1463377807724/1463377836985&file=e9be6771-995b-40eb-a01c-304857a100a1.metadata