Keep in mind that XML is a hierarchy of nodes, including text snippets. The XML you showed looks like this in a tree:
[element] 'text:p'
│
├─[attributes]
│ │
│ └─[attribute] 'text:style-name'
│ │
│ └─[text] 'PS'
│
└─[children]
|
├─[text] 'Prepared by: '
│
├─[element] 'text:tab'
│
└─[text] 'Tim Test'
That should help you visualize how you have to add nodes to your document to get the desired output, eg:
Node, Node1, Node2: IXMLNode;
...
Node := Node1.AddChild('text:p');
Node.Attributes['text:style-name'] := 'P5';
Node2 := Node.OwnerDocument.CreateNode('Prepared by: ', ntText);
Node.ChildNodes.Add(Node2);
Node2 := Node.OwnerDocument.CreateElement('text:tab', '');
Node.ChildNodes.Add(Node2);
Node2 := Node.OwnerDocument.CreateNode('Tim Test', ntText);
Node.ChildNodes.Add(Node2);