where are entrances to walking trails

You can access them when you exit from the 405 onto 4th Street or 8th Street and then making a left turn to drive south, parallel to 405 until you see the signs for Mercer slough

There are trail heads on the west side with parking along Bellevue Way SE but also one the east side asking 118th Ave SE. The east side has a nature center. A bridge connects the two sides.

118th Ave SE has lots of parking and entrances, construction on Bellevue Way has made those access points a PITA

Or off of coal creek parkway as well

Right now you can enter the trail off of 118th near their buildings. The entrance is right across the street from the Access bus area.