To upgrade cart from v1.1.0 to 1.1.1 download this
package, unpack and replace all files of your abantecart by files from "code" subfolder.
To upgrade from 1.1.1 up to 1.1.2 go to abantecart admin section, menu extensions->install extension. Type in field "abantecart_upgrade_112" and press "go".
The same with upgrade to 1.1.3 and 1.1.4... keys for upgrade abantecart_upgrade_113 and abantecart_upgrade_114.
Do not forget do full backup before start.