This will only work if the files you have downloaded were from an Eclipse Workspace. Ffor the transparent bridge, I think not.
Maybe you should try Import/C/C++/"Existing Code as Makefile" project. I don't have experience with this in the esp8266 environment, so not sure what all you would have to do further. Maybe change some settings in C/C++Build and C/C++General to match other working projects.
Hope it helps,
John