help with italics and junk

I tried before, but how do you put italics in your stories? And bold? And underline? And then how do you take it out?

I know there was one like (minus space and all):

<
i
>

and

<
/
i
>
but does that still work on mibba?

Or what?

Haha, it'd be nice if you could help me.
Help much apprecitated. <3

Also, can you center it? Like this
<
center
>

and what about bigg and smaller?

<
big
>

<small
>

<
/
big
>

<
/
small
>

thanks so much much much for helppp everyone <33