At the moment, you would want to get your data into Argos format, which is kind of a weird format for the covariance matrix. There are three columns: Argos.orientation, Argos.semi.major, and Argos.semi.minor.
Argos.orientation is the counter-clockwise angle between the the major axis (of largest variance) and north.
Argos.semi.major is the larger of the COV matrix eigenvalues (variances) divided by 2 and then square rooted (in meters).
Argos.semi.minor is the smaller of the COV matrix eigenvalues (variances) divided by 2 and then square rooted (in meters).
I couldn't run that code without errors and I'm not sure what format your data is in to help more explicitly.
Is this trilateralized or triangulated VHF data? One day, I'd like to find the time to code up support for triangulation in the package, if that's something that people still do.