Well you can't send pictures to people using the forum system- as an attachment to a PM or email that is; you'd just have to get everyone's email address and send it yourself like a regular email.
Posting images here on the forum is simpler probably- just click on the 'Go Advanced' button at the bottom below the Quick Reply text window, go to the second of the 'Additional Options' below the text window, click on 'Pictures Upload' and a new window will open; in the upper right is a button labeled 'Add Files'- click that and you get another window with a button at the bottom in the middle labeled 'Select Files'- click that and you get an Explorer type window that you just find the file(s) you want and highlight them, then click on 'Open'. This adds them to the previous window. When you've added all you want, click on 'Upload Files' which is the second button at the bottom of the window; then at the bottom left of the images window is a button labeled 'Insert Inline' and you get text in the text window that is the command to put the picture in the text like this: [AT TACH=CONFIG]324101[/AT TACH] (I've added a space between the ts of 'ATTACH' so it'll show up as text and not actually put an image in.) Move that text where you want it to be and voila- you have an image posted