1) You will need to create Extended nets or if you have differential nets you would need to create Extended Differential nets. To create Extended nets select the nets on both sides of the capacitor, right click > Create Extended nets. If you need to create Extended Differential nets, then select two Extended nets, right click > Create Extended Differential Pair… You will now see the Extended Differential Pair listed in the SIwizard under the Extended DIfferential tab.