installing from conda-forge

edit

I have now used the info on the conda page of Sage manual in both variants proposed there (1. via mamba and 2. via conda with Python=3.7). In both cases the install seems to be successful but when activating the sage environment and entering it, I tried to follow the instructions in help() and build the tutorial, manual. etc. via the prescribed in the help() line, I ultimately get

sage: tutorial()
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-2-c50b110aacc5> in <module>()
----> 1 tutorial()

/home/lubomir/anaconda3/envs/sage/lib/python3.7/site-packages/sage/misc/lazy_import.pyx in sage.misc.lazy_import.LazyImport.__call__ (build/cythonized/sage/misc/lazy_import.c:3685)()
    351             True
    352         """
--> 353         return self.get_object()(*args, **kwds)
    354 
    355     def __repr__(self):

/home/lubomir/anaconda3/envs/sage/lib/python3.7/site-packages/sage/misc/sagedoc.py in tutorial(self)
   1538             sage: tutorial()  # indirect doctest, not tested
   1539         """
-> 1540         self._open("tutorial")
   1541 
   1542     def reference(self):

/home/lubomir/anaconda3/envs/sage/lib/python3.7/site-packages/sage/misc/sagedoc.py in _open(self, name, testing)
   1519         if not os.path.exists(path):
   1520             raise OSError("""The document '{0}' does not exist.  Please build it
-> 1521 with 'sage -docbuild {0} html --mathjax' and try again.""".format(name))
   1522 
   1523         if testing:

OSError: The document 'tutorial' does not exist.  Please build it
with 'sage -docbuild tutorial html --mathjax' and try again.
sage: sage -docbuild tutorial html --mathjax
  File "<ipython-input-3-aab87ab7e211>", line 1
    sage -docbuild tutorial html --mathjax
                          ^
SyntaxError: invalid syntax

sage:

What am I doing wrongly?