To migrate your Mendeley library to colwiz, you are simply required to input your Mendeley log-in credentials in the import option. Here's how you get to it:
In the desktop library, click on 'import' (top-left).
In the resulting window, select 'Import Mendeley'. You will now be asked to log in with your Mendeley account.
Input your Mendeley credentials in the fields provided and the import process will begin.
Once the process is complete, your Mendeley library along with its PDFs and folder structure will be imported to colwiz. You can now find them under 'All publications'.
Note: Annotations made on Mendeley and private/public group data can not be imported.