There's no "upload" for signatures. You'll need to host the image somewhere like Imgur and then link it in your signature.
https://www.e-cigarette-forum.com/forum/account/signature
Please keep in mind there are restrictions as to what you can and can't have in your signatures.
27. Signature (sigs)
a. No animated graphics are allowed in signatures and there are no exceptions.
b. No affiliate links are allowed in signatures.
c. No commercial links are allowed. This means links to business websites or any website with a primarily commercial objective unless the site is related to electronic cigarettes and is permissible according to other rules. Signatures with links to Unregistered Suppliers and/or sites of dubious quality/content/reputation are subject to removal. If excessive promotion is suspected, an infraction may also be given.
d. Signature images (graphics, gfx) must be 400 x 65px or less in dimension (this means the width cannot be greater than 400px and the height cannot be greater than 65px), and no more than 25kB in filesize. We advise a .gif or .jpg file.
e. Members who are permitted a linked sig graphic cannot also have text links unless there is a usergroup exception for their group.
f. Members may have a 'Stopped Smoking' graphic of standard size in addition to another graphic. Sigbanners of this type may not have adverts either in them or linked to.
g. No links (including in signatures) are allowed to websites we proscribe, or to websites either for, or that feature prominently:
pharmaceuticals, porn, gambling, violence, loans, credit, political parties, religious views, information considered illegal in most countries.
h. A signature is a privilege, not a right, and can be withdrawn any time for any reason and without notice.
