A Flickr account is free (so far) and will allow up to 1,000 photos per user. I have used it successfully for about 4 years.
When you get your account, upload pictures by clicking on the arrow in the cloud at the the top right, next to the search bar.
Drag and drop your photos, or choose them from your file system by clicking on "Choose photos and videos to upload".
Open the picture by clicking on it in your photostream (gallery).
Then click on the curved arrow bottom right corner where there are 4 icons (second from left). You'll get a dialog box called "share 1 photo to".
Make sure bbcode is selected just under the "share 1 photo:" script. It should have a blue line under it.
Select the size you want in the drop down menu. Large 1024 x 690 is good.
Left click the URL to highlight it and press Control + C (hold control and then add c) OR left click to highlight the URL then right click the highlighted URL and choose copy. This copies the URL.
Go to your post and add the URL by Control + V (hold control and then add v) OR right click in the box and choose paste. This pastes the URL.
Click reply at the top right corner of your post, NOT quick reply at the bottom left. If you don't see your picture in your reply BEFORE you submit it, select "BBCode", then switch back to "Preview" and it should show.
Then click on create post.
Check the thread on this tech section concerning posting photos via Imgur, as an alternative to Flickr. I got to my max on Flickr and moved over to Imgur. It's free, similar, and a bit easier to use, imo.