Blurr background layi aperture number lowest rakho. Meaning, camera lense poora khool ke picture click kero.
For beginners a good prime lens to use is Canon / Nikon 50mm f1.8
Aperture value is denoted by f
you can use Aperture priority function on your DSLR ( Av on canon, and A on Nikon camera)
Use the scroller to set it to the lowest value
the scale of f value and the lens opening goes as below
Value (low to max)
f 5.6 -------------------f 22 (just for observation)
Lens opening
( )---------------------- o (from wide open to least )
If you set aperture to lowest value say 5.6 , lens will have full opening ( depends on the range)
if you take a photo focussing on particular object at lower f value, the background will get blurred.
This technique will work for Bokeh effect too.
Example of aperture priority on basic 18-55mm lens