How can i monitor the Mikrotik router performance (HD, Memory, CPU, ... etc).

Tool-> Graphic -> resource Rule - > Add + 0.0.0.0/0

When write Ip router and select graphic , will show cpu and HD and ...etc .

/tool graphing resource
add allow-address=0.0.0.0/0 disabled=no store-on-disk=yes

where do i have to write the router IP ?

explorer, oper, mozilla... choose your favorite graphical browser. anything starting with an old netscape will do.

of course, you could use more sophisticated apoproach, like SNMP monitoring, or setting up an MT dude somewhere.. but for monitoring 1 single appliance it would be an overkill.