1. Clone wallet sources
git clone https://github.com/valentinecoin/valentinecoinwallet.git
2. Set symbolic link to coin sources at the same level as src. For example:
ln -s ../valentinecoin cryptonote
Alternative way is to create git submodule:
git submodule add https://github.com/valentinecoin/valentinecoinwallet.git cryptonote
3. Build
mkdir build && cd build && cmake .. && make