Thanks! I added:
sudo apt-get install libssl-dev

But now I get
"make -f makefile.unix
g++ -c -O2 -msse2 -pthread -Wall -Wextra -Wformat -Wformat-security -Wno-unused-parameter -g -DBOOST_SPIRIT_THREADSAFE -I/home/me/yacoin/src -I/home/me/yacoin/src/obj -DUSE_UPNP=0 -DUSE_IPV6=1 -DSCRYPT_KECCAK512 -DSCRYPT_CHACHA -DSCRYPT_CHOOSE_COMPILETIME -DHAVE_BUILD_INFO -fno-stack-protector -fstack-protector-all -Wstack-protector -D_FORTIFY_SOURCE=2  -MMD -MF obj/alert.d -o obj/alert.o alert.cpp
alert.cpp:244:1: fatal error: opening dependency file obj/alert.d: Permission denied
compilation terminated.
make: *** [obj/alert.o] Error 1"

Any tips. Sorry, but still Linux noob here, but learning fast.