Wire a link to a specific interface
The interface picker pre-selects the first free port on each node, and for a simple lab that is usually right. When it is not - you need Gi0/2 specifically, not whatever is next in line - you can change both dropdowns in the picker. Ports already in use are greyed out, so you can not wire one twice by mistake.
eth1 is already wired between SW1 and R1 (greyed out, marked "used"). Open Links → Draw link, click SW1 then R1 - the picker defaults both sides to eth2, the next free port.
Override each side to the exact interface you want - here eth3 on SW1 and eth2 on R1, two different port numbers on purpose (common when you need one particular port on one side). Click Connect.
The new link is drawn immediately - and it really used the interfaces chosen, not the picker's defaults.
This matters most on devices with named, meaningful ports - patching a lab to mirror a real rack where "the uplink goes in Gi0/1" is a deliberate choice, not an accident of drag order. See "Add a link while the lab is running" for the same picker on an already-started lab.