How can I make lawn more porous it is very slushy with water puddles

Rent an aerator, which will take plugs out of your lawn. Fill with sand.

You can also purchase at your hardware store a spreadable compound that makes clay soil break down and drain easier...we had same problem.

To amend clay soil add top soil,pelletized lime,and Gypsum

BIU

Put in Fench drains around your lawn. Our ground has a lot of clay. My huband borrowed a trencher from work. Put in gravel and drain pipe and a driain at one end. At the other, he let it be open . When it rains, ter pours out the other end.

If your soil is not clay, you can rent an ariater for lawns. It pulls behind a lawn mower and punches wholes.

Our lawn was so spongy, ur building was tipping.

I found gypsum is a very good starting point... along with aeration, then at a later time compost & topsoil amendments... can get tedious, but you may need to stay with it for a few seasons (or years).

Dig in Fork all over