I'm very new to DSLRs and I was wondering how to make it so that my Nikon D3300 focuses but does not blur anything out like when it focuses on a flower or something and it blurs everything else around it. I have been trying to figure it out but with no luck.
Like with any other camera you stop it down to a small aperture like f/22, say, of course it depends on the background distance as well. If you go that high, though, you will get light diffraction which will be apparent. The larger the aperture the shallower the depth of field; that is why big apertures like f/1.8 and f/1.4 are usually used for portraits to separate the subject from the background and give a nice bokeh.