update readme

README.md

@@ -65,6 +65,7 @@ make -j 16
 
 ## Usage
 ### 3/28 update
+0. Git switch to multiple_top branch.
 1. Use `example/top-thermolastic-compare-3d` to run mechanical(Me)/mechanical thermal(MeTh) topology optimization(Top) and simulation(Sim).
 The procedure run in following order: 
    1. Me Top & MeTh Top -> density(*_MeTop_rho.vtk & *_MethTop_rho.vtk) and compliance/volume each iteration(*_MeTop_compliance.txt *_MeTop_volume.txt & ...)