Below is the advice I was given by Mike, it works for me.
Using Postimage site.
You need to create a free account on the Postimage site, and then upload your pictures on it.
Then select your pic that you want to post on the forum.
Look for the 'share' button and choose 'hotlink for forums' option. This is the last but one choice.
Click on the clipboard symbol on the right to copy the link.
In your post, paste the link. I use this on my lap top. That's how I do it anyway.
If you just use the 'add image to post' with the 'p' in the blue box beneath the 'post a reply' window, you only seem to get a small image in your post.
On Ipad or mobile phone, I would imagine it's the same, but I'm using the Tapatalk app. So I simply use that application, and you just select large, medium or small size pic when posting from this.