Error building it

[wjuniorhp]

Following the Build instructions, an error occur at the "cmake .." step. The message reads as follows:
cmake ..
-- The C compiler identification is GNU 7.3.0
-- The CXX compiler identification is GNU 7.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at /usr/share/cmake-3.10/Modules/FindX11.cmake:429 (message):
Could not find X11
Call Stack (most recent call first):
CMakeLists.txt:7 (find_package)

-- Configuring incomplete, errors occurred!
See also "/home/well/xlayoutdisplay/build/xlayoutdisplay/build/CMakeFiles/CMakeOutput.log".

[wjuniorhp]

I misundestood the issue