It's not possible to use the word 'like' without an object : you always have to 'I like [something]. The word 'here' cannot be an object because it's an adverb, not a noun. You can't say 'I like here', because there is no object in this sentence. So we put the word 'it' in this phrase as a kind of 'dummy object'. It's the same as saying 'It is nice here'. The word 'it' doesn't refer to anything specific : it is just there to support the verb. You can understand the sentence as a whole as 'I like being here.'

because "here" is an adverb of location

In English, the verb "to like" requires a complement. You always like SOMETHING (= it) or someone (you/him/her/them). When the complement is not clearly stated, you use one of the ponouns I mention above. Check it out: I like my sister very much. = I like HER her very much. I like studying English on this website very much. = I like IT here very much. Best wishes, Guilherme.

Hi, please read the section "13. What is a personal pronoun?" https://books.google.com.au/books?id=0H0LpATiLxwC&printsec=frontcover#v=onepage&q&f=false

For it; it means the thing that you love him here