Sorting parallel arrays in C++

[2kaud]

any suggestions as to what I'm doing wrong here...

Yes - your data structures. If you include the arrays within the structure, then you don't need an array of BorData. You have either
1)

struct BorData {
     string borough[5]={"New York City","Bronx","Queens","Brooklyn","Manhattan"};
     int accidents[5];
};

...

BorData combine;

or 2)

struct BorData {
     string borough;
     int accident;
};

...
BorData combine[5] = {{"New York City", 0}, {"Bronx", 0}, {"Queens", 0}, {"Brooklyn", 0}, {"Manhattan", 0}};

Which way you choose then determines how you use the data.
for 1)

for (int i = 0; i < 5; i++)
{
     cout "..... " << combine.borough[i];
     cin >> combine.accidents[i];
}

for 2)

for (int i = 0; i < 5; i++)
{
     cout "..... " << combine[i].borough;
     cin >> combine[i].accidents;
}