Bootstrap is Framework which helps you to develop mobile friendly web applications, You don't need to learn it just visit the BootStrap SIte click on the get Started and copy the starter template.
Past the starter template on a blank HTML page and start putting the all the bootstrap components in the body section of the starter template.
All the component's codes are already shared on the official site of the bootstrap you just have to copy and paste the code on you page at required location and edit it according to your requirements.
There are two methods to use bootstrap in your project online and offline I have discussed both in the video lecture above but I personally prefer the online method which is lite weight.
Using bootstrap with .NET 6 MVC is prettey straight forward no matter if you are using Online or offline method all you need to replace the _Layout.cshtml file with start template code and put back the
Function under the body of Layout.cshtml file.
It is recommended to watch the video lecture for proper understanding.