Your question does not specify what you want to do :

- Adding a new object to the same figure.

This is done with the `+`

operator (and the related `+=`

operator) :

```
sage: G= Graphics()
sage: G+=plot(sin,(-pi,pi))
sage: G+=plot(cos,(-pi,pi))
```

gets you a figure bearing two curves.

- Adding a new figure to a graphic object holding figures.

This is done by creating a `GraphicsArray`

object from the list of graphics you want to display :

```
from sage.plot.multigraphics import GraphicsArray
sage: G=GraphicsArray([plot(sin,(-pi,pi)),plot(cos,(-pi,pi))])
```

gets you an object holding two figures bearing one curve each.

Note that you (currently) *can't* append a new figure to an existing `GraphicsArray`

:

```
sage: G.append([plot(exp,(-pi,1))])
---------------------------------------------------------------------------
NotImplementedError Traceback (most recent call last)
<ipython-input-57-a77afab4c542> in <module>
----> 1 G.append([plot(exp,(-pi,Integer(1)))])
/usr/local/sage-9/local/lib/python3.8/site-packages/sage/plot/multigraphics.py in append(self, g)
1272 """
1273 # Not clear if there is a way to do this
-> 1274 raise NotImplementedError('Appending to a graphics array is not '
1275 'yet implemented')
1276
NotImplementedError: Appending to a graphics array is not yet implemented
```

HTH,

If possible, please provide a minimal example to reproduce the problem.