I am using Mcrosoft 2007, but this will work with older versions as well.
Step 1. scan the cartoon and save as jpg
step 2. Open Microsoft word and go to 'insert' on the menu bar above. select 'picture' and a window will open.
step 3. find your saved cartoon and hit the 'enter' button or click 'insert'. now your cartoon is on the page. If you click on it, a menu for picture editing will appear on the menu bar and you can crop and do many other things to the cartoon.
step 4. Go to insert on the menu and select Shapes. You will see 'callouts' as the second last item on the menu that will unfold. A callout is actually a text baloon. Type your text directly and then move the callout object to the desired position. You can adjust it by picking its different points. This way you can direct the speech to the guy talking.
If you want other kinds of text and explanations on your cartoon, follow this instructions,
Step 5. Go to Insert on the menu bar and select 'text box'. You will get several options, including the option to draw your own text box. Draw your own by using the cursor to mark out a box.
Step 6. The box you have marked out will be crying out for text so write something in it. You can stretch it by pulling its corners. You can also move it to the most appropriate position.
Stetp 7. The box will come with an outline. If you do not want the outline, Click on the outline on that box and the menu above will change to give you options for colour etc. Besides the colour options, there is a button for outline. Select it and then select 'no outline' in the menu that will unfold. You can also make it transparent so that it does not hide images on your cartoon.
To make it transparent, click on its edge (twice if the colour themes do not show on the menu bar) and then select 'no fill.'
All the best with your cartoons.