Assuming you installed boost yourself cf.
http://www.boost.org/doc/libs/1_61_0/more/getting_started/unix-variants.html, after running bootstrap.sh, you would run
./b2 install
This is not enough for graph-tool, and to install iostreams as well, you would run
./b2 install --with-iostreams
When installing graph-tool on CentOS 7, after this I also had to install --with-coroutine, and a few more (which I do not remember).
The above answer is somewhat generic, but seeing that you use Ubuntu, it may be that your package manager allows you to do this more easily, for example using a command like
sudo apt-get install libboost-all-dev
Good luck!
Frank