Sending a letter from the US to Japan

I have an address for my japanese host family but i am still confused about how i should put it on the envelope. Also, is it okay to print out an envelope? I do not know how to write in Japanese.

Here is the adress with numbers changed:

神奈川県 逗子市 久木7-10-25

You'll have to translate the address into Romaji at least with the Postal Code and Country name : JAPAN for the international postal services to know how / where to send it.

You can also have Kanji / japanese as is, but some parts will need translated for the postal service to be able to know which country to send it to.

Yes, it's fine to print an envelope.
Since you have the address written in kanji right there, you can print that onto an envelop just as it is, of course with the recipient's name below it, and the word "Japan" at the end :)

If you want to write it out in romaji, you could also write:
(name)
X-XX-XX Hisagi, Zushi-shi,
Kanagawa, 249-0001 Japan

"249-0001" is the postal code for Hisagi. But you don't have to have it, as you have the full prefecture name and everything :)

You have a perfect Japanese address, just print it out and paste a copy on the envelope, and add ''to JAPAN'' at the bottom.