DavidR
2
There is no rush to delete anything from the chest, a protected area where it can do no harm. Anything that you send to the chest you should leave there for a few weeks. If after that time you have suffered no adverse effects from moving these to the chest, scan them again (inside the chest) and if they are still detected as viruses, delete them.
You need to open the avast chest, start as if going to run an on-demand scan, click the menu and select virus chest, Infected Files, here you will find those files you sent to the chest. They can be rescanned from within the chest and deleted, etc.