Quite often people ask me how and why I stretch my own canvas. I like to do things the old fashioned way and I believe stretching my own gives me a better control of the quality of my finished product. Yes, it can be time consuming, especially when making larger canvases but I like the result.
I also coat my canvas at least 3 times with Gesso primer before applying any oil paint, which ensures a sound ground on which to lay the paint. Gesso enables the paint to adhere to something and not seep or bleed through the material of the canvas.
Instead of trying to explain in words I thought I would pass on this link I found on the Blick website.
Hope this is helpful in answering the question of how one stretchers a canvas!
This photo is at least 6 years old but it is fun to recollect the conditions I managed to produce work in, during my early days as an artist!