a probably very basic question

I don't know if i am missing something or what. I love all the icons that i have gotten from people, and i am anxious to use them in my lj (credited of course). But my lj (free acct) won't let me put any icons that are over 40 KB, and i have noticed that almost every icon i have gotten is, like, 70 to 90 KB and more.

I know these icons have been made for lj, so how does one put them IN lj?

Thank you in advance for answering this probably really basic question. (I can't find any reference to it in the frequently asked questions section).