Hi Akash,

Because of a charged spherical shell, change is not there within the empty space enclodes by the shell. The symmetry of the problem sir just sperical Gaussian surface inside the shell Centered at the centre of the shell.The charge enclosed by such gaussian surface is zero.

Hence electric field at each point of the Gaussian surface is zero. this is true for all Gaussian surface is having the radii between 0 to R 

Where R is the inner radius of the shell. Therefore electric field inside a uniformly charged insulating surface is Zero.

There are two cases Hollow sphere or Solid sphere, But here we will consider Solid Insulating sphere as analysis of Hollow sphere is trivial and which is similar to a solid conducting sphere.

Unlike conducting sphere where all the charge resides on the surface of Sphere, Here charge will be distributed inside the sphere as well because it is an insulating sphere.

Now it is uniformly charged so You can assume its charge density to be constant let it p.

Now at any distance r from the center but inside the Solid Insulating sphere We can find electric field using Gauss Law

Electric flux enclosing an imaginary sphere of radius