Use the LoadFromArrays method on a range. The first cell where the arrays values should be set on the row is used to create the range.
The argument passed to LoadFromArrays is an IEnumerable of object arrays, so the values to set on the row should be first converted to an object[] and then wrapped as an IEnumerable 
int rowNumber = ...
int columnNumber = ...
IEnumerable<object> values = ...
var range = ws.Cells[rowNumber, columnNumber];
range.LoadFromArrays(AsEnumerable(values.ToArray())); 
/* ... */
// see http://stackoverflow.com/q/1577822/614800 for a discussion on how
// to wrap an object into an IEnumerable
private static IEnumerable<T> AsEnumerable<T>(T obj)
{
    yield return obj;
}