If you want to add pictures from your computer, click on the 'Go Advanced' button on the lower right of the reply box. Under 'Additional Options' there is a selection to manage attachments. Just click on 'Add Files' and that will open the download window. Press 'Select Files' to go to your computer and look for your pictures. You need to know where they are located. Select a photo and it will upload.
The other way is a lot easier. Just open the photo within your photobucket and choose the share option. That should give you the link address. Simply copy that address and paste it into the reply window here. Use the square bracket [ and ]. Type
I simply use Photobucket. Load the pics there, move the curser over the pic and a drop down will appear. Left click on the bottom one that is "IMG code" then come to the forum and when you want to paste it here just hold down your "ctrl" key and tap the "V" key and it will insert into your post. Quick and easy.