Coollant level low

[Pammella]

How do I add more cooolant to my 745li 04 and wgich brand should I use?

[shogun]

that is most probably shown in the owners manual? At least in the owners manual of my old 1988 E32 750iL.
there is the cooling water expansion tank, see here the drawing
Radiator
remove the cap and fill in.
Owners manual tells you which coolant you need, the dealer has it. If in doubt, use BMW coolant.
read this thread
Coolant leaking from the weep hole 2002 745i - Bimmerfest - BMW Forums