I noticed in the tutorial that it doesn't give an upper limit on the photo size. They can be too large for the BBS system to handle. Because, the content management system I use, WordPress, cannot handle images greater than 5Mpixel, I size all my images to 5Mpixel for web use. Most cameras these days produce 16Mpixel images or larger. These are too large for most web based image management systems; or at least larger than the site owners want to handle.
I use Lightroom to process and resize/reformat images. I don't know what might be available inexpensively to do the same thing. If I wanted the current Lightroom/Photoshop (I use older versions) , available only on the cloud, it would be $19.95 a month. Adobe is licensing everything by the month now as it's software is only available in the cloud. Of course, you could only pay for a month and cancel if you only need it every once in a while All the other Creative Suite apps; Illustrator, In-Design, DreamWeaver, Acrobat, Flash, etc...; are all available from the cloud on a monthly subscription basis.
If you have Dropbox, you can upload photos there and insert the link they provide you between the img /img (brackets omitted) tags in your post. I do that with Amazon S3. There are literally dozens of cloud based storage systems these days that should let you do the same thing. If you can upload a file to one of these services, you can post it in a message.