Modify md file for some batch delection operation and change some pictures

docs/user_guide.md

@@ -102,7 +102,7 @@ You can add members with different roles to an existing project. You can add a L
 ![browse project](img/new_add_member.png)
 
 ### Updating and removing members
-You can update or remove a member by clicking the icon on the left.  
+You can check one or more members, then click `MEMBER ACTION`, choose one role to batch switch checked members's roles. You can also click `MEMBER.REMOVE` to batch remove checked members.
 
 ![browse project](img/new_remove_update_member.png)
 
@@ -162,7 +162,7 @@ Entering a keyword in the search field at the top lists all matching projects an
 
 ## Administrator options  
 ### Managing user  
-Administrator can add "Administrator" role to an ordinary user by click button on the left and select "Set as Administrator". To delete a user, select "Delete". Deleting user is only supported under database authentication mode.
+Administrator can add "Administrator" role to one or more ordinary users by checking checkboxes and clicking `SET AS ADMINISTRATOR`. To delete users, checked checkboxes and select `DELETE`. Deleting user is only supported under database authentication mode.
 
 ![browse project](img/new_set_admin_remove_user.png)