What is the correct way to connect bootstrap locally if I am using Gulp and scss?

Question

Bootstrap

Please tell me, I have already shoveled the entire Internet in search of information, and I can not understand how to do it correctly. I work in Gulp and write styles in scss, and the compiled file goes to production, I connected the bootstrap to the css folder where scss is compiled and naturally connected to it in head, but as a result, in the production project, I got an error and the file from there at all disappeared. Explain to me how to connect correctly?