Nothing wrong with that.
Next time, here are my steps - so simple, even I can follow them.
1 - on the web, find the photo you want
2 - RIGHT click on the photo and select "View Image"
3 - when it comes up in its own window, copy the URL at the top.
4 - now, go into SailNet and start your post
5 - where you want your picture, up above, click the little square yellow icon that sort of looks like a picture
6 - in the new little box that comes up delete what is there and put your new URL into it that you copied from your picture
7 - click Go Advance at the bottom to make sure it is not a compromising picture of your crew and if you like it - click Submit Post
Try it - it might even work.