I would approach by finding top dead centre - line up appropriate mark on crank pulley wheel with TDC mark (depending on age and variant - then either lower mark on timing belt cover OR separate TDC pointer mark) - cylinders 1 & 4 should be at maximum height (double check) and holes on cam wheels lined up with lugs on cam boxes. With engine in TDC position then distributor rotor arm should be at a position corresponding to contact in cap that feeds ignition lead to no 4 cylinder. Exact ignition timing can be set by slight adjustment of distributor body back/forth with engine running. Make sure plug leads are sequenced in correct firing order 4,2,1,3 .......
