Adjusting document's margins:
Click Document -> Preferences... menu and in a dialog box that pops up, from the list
on the left hand side select Margins.
There in the central part clear Default margins checkbox and set your custom margins:
Top, Bottom, Inner, Outer.
Useful keyboard shortcuts:
CTRL+SHIFT+Space - inserts small vertical space
CTRL+R - document preview exported to specified format
CTRL+Space - inserts hard horizontal space
Alt+M F - inserts a fraction
Alt+M = - inserts an odds sign
Alt+M E - inserts a power
Alt+M X - inserts a bottom index
Alt+M S - inserts a square root
Alt+M R - inserts a root of specified degree
ALT+M C I - adds a column in the table on the right of current column
ALT+M C D - removes currrent column in the table
ALT+M W I - adds a row in the table below the current row
ALT+M W D - removes currrent row in the table
How to insert a symbol:
Click Insert->Special character->Symbols... menu.
After you insert a curly bracket expression (available in the math toolbar) a new expression line can be inserted by pressing CTRL+ENTER.
Custom space between sequential lines of document text you can define here:
Document->Settings...
In the list on the left hand side you choose option: Text layout and in the center of the screen
you can set leading setting.