Head up to the 'quick links' option on top of the screen.
Here you can select editing avatars & signs. Concerning avatars you can pick a standard one, or make a custom. Maker one with dimensions close to a square inch and use the avatar-creator from this site. This will adjust the resolution and size to make it suitable.
For Signs; make an image no more then 450 by 150 pixels, and no lager than 30 K (putting resolution to 72 pixels/square inch makes it possible to use the full allowed size). Go to edit sign, select your image from your comp, upload it and you will receive a code. Paste that in the options screen you will be lead to and presto.
You can attach images in post by selecting 'preview' at the bottom of the screen after you have written your post. Here you get the option to include images from your PC. These have to be below 250 K to fit in.
Setting a signature (under your post)
Getting a picture under your username
Click 'post reply'. To attach a file to a new post, click the [Browse] button at the bottom of the post composition page, and locate the file that you want to attach from your local hard drive.
Only certain types of files may be attached: these are the valid file extensions for files to be attached to this board: gif jpg txt zip jpeg.
or
Surround the address of the image with the image tags: [img]http://www...[/ img] (without the space between the slash and img) 😉
Ceterum censeo OTF esse delendam.