I followed the instructions and it still didn't work.
Ok, let's take this step by step then.
1. Take out the spaces after the < and >. So take out the space between the < and img, and the space between Y and >.
2. Go to your gif, right click, click copy image address.
3. Replace filename.gif with the image address. (KEEP THE QUOTATION MARKS ---> " ")
4. Put in dimensions of the gif where it says width and height (300 for width and 200 for height)
Make sure you're doing it in a journal and not a comment. It doesn't work in comments.
I can't help you any further unless I record my screen for you. You don't even need premium membership.
Here, take this one I premade. It has everything done, all you have to do is replace the gif with one of your choice. Copy and paste the link below into your journal and click preview. You should see a gif.
<img src="33.media.tumblr.com/06cdcf5cbf…" alt="alternative text" width=300 height=200>
1. Take out the spaces after the < and >. So take out the space between the < and img, and the space between Y and >.
2. Go to your gif, right click, click copy image address.
3. Replace filename.gif with the image address. (KEEP THE QUOTATION MARKS ---> " ")
4. Put in dimensions of the gif where it says width and height (300 for width and 200 for height)
Make sure you're doing it in a journal and not a comment. It doesn't work in comments.
I can't help you any further unless I record my screen for you. You don't even need premium membership.
Here, take this one I premade. It has everything done, all you have to do is replace the gif with one of your choice. Copy and paste the link below into your journal and click preview. You should see a gif.
<img src="33.media.tumblr.com/06cdcf5cbf…" alt="alternative text" width=300 height=200>
Oh okay I see what i was doing wrong now. I kept removing ALL spaces when there needed to be some spaces in it. the instructions got a bit confusing until you broke it down. Thank you so much 
You're very welcome! Have fun! 