Contacts Sidebar

Z 4 z 5 gwězdkow pógódnośony

wót Peer55 dnja Sept. 24, 2017 · trajny wótkaz

Stephane I just read I could download contatcssidebar-1.7.1.zip. I've done it.
But how should I install it? It's not an add-on for Thunderbird. I've still got:
XML-parse error: undefined entity
Location: chrome://contactssidebar content/contactsPanel
xul nr 250 col. 9
<label value="&searchInput.label;">
Please note I'm not a Win user, I'm an Ubuntu Linux user. But I don't there's much difference. Pls advise how to install everything in the zip-file.