Your code must fill the rchild and lchild data with another tree.
struct treenode *lnode = malloc(sizeof(struct treenode));
lnode->data = ....
(*pp)->lchildstruct = lnode;
Best is to write some time-saving functions like
struct treenode *treeWithData(int data);
void setLeftChild(struct treenode *node, struct treenode *lNode);