Your problem requires to to ask the user for two numbers and then loop from the lowest to the highest. Try doing the 'ask the user for two numbers' part first.
#include<iostream>
using namespace std;
int main()
{
int a,b,f,y=0;
cout<<endl<<endl<<endl;
cout<<"Enter an integer: ";
cin>>a;
cout<<"Enter a greater integer: ";
cout<<endl<<endl;
cin>>b;
for( int x=a; x<=b; x++)
{f= 3*(x*x)+2*(x)-4;
cout<<"x= "<<x<<" then f(x)= "<<f<<endl;}
cout<<endl<<endl<<endl;
for( int x=a; x<=b; x++)
{y= y+x*x;
cout<<"x= "<<x<<" then x^2= "<<x*x<<endl;}
cout<<endl<<endl<<endl;
cout<<"The sum of the squares from 1 to 8 is: "<<y<<endl;
system("pause");
return 0;
}