How to become a ipfs node?

we have two questions:
First,we have stable net Network bandwidth and Large data storage space,and we find that we can connect to the ipfs ,but there is no data storaged,who can tell me why?
Second,My frend faraway upload files into ipfs,but the smaller file sized 1M,I can downlad it ;another file sized 100M,we cannot download to optimization my computer

IPFS will only host data that you tell it to and only download files that you tell it to. So if you want to host content for the network you will either have to; pin something that you have stored locally via “ipfs add [file]” or “ipfs add -r [directory]” to host a directory and all of its sub directories; or if you want to download and host something “ipfs pin add [hash]” for a file or “ipfs pin add -r [hash]” to recursively download and host a file tree and all of its components.

As far as optimization is concerned, do you have TCP forwarded on port 4001? Or if that isn’t it, you may be able to have your friend announce to the DHT that he is hosting the 100M file that you are interested in. I’m not sure if this could help but I don’t think it could hurt. He would do it like this “ipfs dht provide [hash]”. Also consider that your friends upload ability is more likely the problem than your download ability.