Inserting images in Joomla is not very intuitive by design. However, using the following methods can make things easier. The first set of instruction is for the native Wysiwig that comes with Joomla.

1.Paste the images needed for the site in the appropriate folder. Resizing can be done before or using the Wysiwyg editor native to Joomla.

2. Go to site>>media manager menu.

3. Go find the image you are looking for.

4. Click on the image, the URL will show up in "Image/Url Code" input box automatically.

5. Copy the URL but erase the beginning and end par( in red)t as shown in this example:

<img src="http://localhost:85/enu/images/BannerJune16_08.gif" align="left" hspace="6" alt="Image" />

This is the proper code you will be left with:

http://localhost:85/enu/images/BannerJune16_08.gif

just the plain URL path, could be offline or online

6. Open the editor and click on the small "images" icon in the Wysiwig editor.

7. Paste the URL copied above into the URL window and click on apply.

8. After that, click on the image again and you will be able to edit the position, alt tags, description AND size.

Update:Just use the new JCE editor, it's intutive and has many more options.