Smartness is a multi-dimensional attribute. For example, a smart motor mechanic and a smart software developer are both smart in their respective fields, but neither is likely to be seen as smart in the other person's domain.

As a very broad brush generalisation, you become smart by learning from those who are smarter than you in your chosen field. You could accomplish that by reading, seriously studying, being mentored and most critically practising your "craft".

If you simply just learn a huge pile of facts and are able to regurgitate them at will, then most people will think you are a "smart alec", which is probably not what you want to be known as.