Constructing constant curvature metrics on Riemann surfaces with singularities

By constructing an ODE through a kind of meromorphic 1-forms, we will give an explicit construction of a kind of conformal metrics of constant curvature on Riemann surfaces with singularities. As an application, we will classify constant curvature one metrics on $S^2$ with two conical singularities, which was first proved by Troyanov in \cite{Tr89} by using projective connection.