Anyway, since you're a newbie you can not use the feature I think unless you pay for the 'copper' membership.
More properly, iirc, the user cannot put there anything else than short plain text if he's newbie.
In time, with more and better posts, while ranking up, the signatures are getting allowed to get bigger, nicer, colored, with links, ...
Indeed, copper membership can allow some more for styling, but still not the "full package", from what it tells here:
Additionally (and these might change depending on how things go), Copper Members currently have these bonuses:
- Some of the same permissions as Member-rank members, such as reduced signature styling restrictions.