I want to use forum in my projects for increase traffic but I don't know how to use signature in forums according to last Google updates about seo. Please guide me.
Most forums will be no follow, so it doesn't really matter. For those that are not use keywords for anchor text. Use different ones/words on different forums.
Also if you use related forums (to your niche!) it would be great! Also, do NOT just add your website in your profile! Try to be as active as you can, this is the key to get full benefit of forums!
Firstly, I suggest you read Google's Webmaster Guidelines. They provide forum signature links as an example of link schemes. https://support.google.com/webmasters/answer/66356?hl=en So, based on this I would avoid using keywords in signature links and either use raw URL or the brand name (unless the so-called brand name is in fact a keyword name). I wouldn't recommend thinking about search engines when it comes to forum signature links and instead use them to market to forum members.
Remember that forum signatures has been weigthed much lower, so it does not give the same effect as before. Very often forum signatures are nofollow too.
Now forum post weighted is much loser but if you work on the niche forum then you can use the hyperlink in signature section. If you are not working on niche or relevant forum then you can do it into the forum post body like a contextual link. It will boost up the ranking of your keyword never use link in signature if you are working on non relevant forums.