Let me see if I can help. A lot of people don't know how to post images here, so maybe this will help them too.
Step 1.
When writing your reply or new post click this button to insert an image.

Step 2. When you click on that button it will bring up a box that looks like this.

Step 3. Paste the URL of your image into the source field. Using the example of the thumbs up I provided above, cut and paste https://i.imgur.com/I73pxYz.png into the Source field so it looks like this.

Step 4. After you have pasted your image URL into the Source field, hit the tab button on your computer once to skip the Image Description. Doing that will take you to the Dimensions fields. As you can see, it automatically determines the size of your image. In this case, it is 144 x 144 pixels.

Step 5. Now say you think 144 x 144 is too big. Simply type 50 in the first Dimension box and hit your tab button once. Since Constrain Proportions is checked by default, it will fill in the other 50 automatically. Now you simply hit the ok button and you get this inserted into your post.
