NSMutableArray *array; array = [NSMutableArray new]; [array addObject: anObject];
Assuming anObject is an NSObject (but not nil, remember, you can't put a nil object into an NSArray). As usual, anObject is RETAINed when it is added to the array.
If you want to insert an object into an array at a certain position, you can use insertObject:atIndex::
NSMutableArray *array; array = [NSMutableArray new]; [array addObject: @"Michele"]; [array addObject: @"Nicola"]; [array insertObject: @"Alessia" atIndex: 1]; /* Now the array contains Michele, Alessia, Nicola. */