mvc asp.net visual studio how to override bootstrap.css file

M trying to build a website using Mvc asp.net in Visual Studio 2013. I've bundled my css file-'style.css' to the project, but my website has undesirable white spaces and margins around headers and other important elements, in spite of setting margin:0 in my css. I found that the bootsrap.css file that is in the project by default is causing this. How do i override the bootstrap.css file? Because it is for main elements like header and container, being specific does not help. M a beginner in this. Please help me with a solution.