1) Open the OCE GUI.
2) Select Managed Resources>Elements and filter so that only the ones you need to modify are viewable.
3) Use Ctrl/A to highlight all elements in the list.
4) Right-click and select Edit Element.
5) Select the "Mass Modify" checkbox next to Read-Write Community or Read-Only Community.
6) Enter the new string in the text box.
7) Click Apply/OK.
8) Verify that the strings have been changed/added. If the fields are not present, right-click on the grey title bar and chose Select Fields to add Read-Only Community and/or Read-Write Community fields.
Then monitor your polling errors under Polling Management to be sure the devices are being successfully polled using the new string.
nhListElements -where "readCommunity matches test" - nhModifyElements -fieldName readWriteCommunity -value test1
The command above assumes that "test" was the original community and "test1" is the new one.