update README.md

README.md

@@ -1,8 +1,32 @@
 # zotero-snap
-snap for zotero
+[![zotero-snap](https://snapcraft.io//zotero-snap/badge.svg)](https://snapcraft.io/zotero-snap)
+
+Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share your research sources. Zotero has its offical linux publish version, but to simplify the rather difficult installation on linux systems, we have released zotero-snap which can be installed directly from the snap store.
+
+## Install zotero-snap
+
+If your system satisfy the **Snap pre-installed list** from [this documentation](https://snapcraft.io/docs/installing-snapd), you can directly click the installation link below and install zotero-snap.
 
-Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share your research sources.
 
-[![zotero-snap](https://snapcraft.io//zotero-snap/badge.svg)](https://snapcraft.io/zotero-snap)
 
 [![Get it from the Snap Store](https://snapcraft.io/static/images/badges/en/snap-store-white.svg)](https://snapcraft.io/zotero-snap)
+
+
+
+If your system does not pre-install snap. You can follow the instructions below to install snap and snap for zotero.
+
+Open Terminal and install snap.
+
+```
+sudo apt install snapd
+```
+
+Install zotero-snap
+
+```
+sudo snap install zotero-snap
+```
+
+## Update
+
+If zotero automatically top up a window that reminds an update, likely with *Unable to update, no permission* description, you can just kindly close the window and wait for one day or two, as snap will automatically detect and update the zotero new version.