To become Jr Member all I need is 30 activities?
Which is 30 posts during a period of 30 days, right?
yes your right! you need 30 activity to rank up to jr member. you can become jr. member in less than a month.
Where do you think I can ask such question?

I don't want to keep losing my comments just because I don't know where to ask

there are several thread around forum that will help you. If its only about begginers question you can go and ask here
https://bitcointalk.org/index.php?board=39.0