Add Element inside of an element XML VB.NET

How can I add an element inside of another element. Im sure this is easy but I cant seem to find an answer in vb.net. I pretty much need a file that looks like:

<Crop>
     <Name>CropName</Name>
     <Field>
        <Name>FieldName</Name>
           <Expense>
              <expense1></expense1>
              <expense2></expense2>
           </Expense>
     </Field>
</Crop
<Crop>
     <Name>CropName1</Name>
     <Field>
        <Name>FieldName</Name>
           <Expense>
              <expense1></expense1>
              <expense2></expense2>
           </Expense>
     </Field>
</Crop

I also need help adding to this. So lets say I want to add to the crop called 'CropName1' and add another field element like I already have inside 'CropName1' then how would I do that in vb.net. I am open to use linq or whatever. Example code would be great help. Please don't give me a link to a tutorial on LINQ and xml. I know how XML works just not sure how to do this particular problem and thought I could get some sample code from you all. Thanks!