You really need to try these on to see how comfortable they are.
I recommend slipping them on, then you'll see how nice they feel.
この場合、次のような言い方ができますよ。
ーYou really need to try these on to see how comfortable they are.
「どんなに履き心地が良いかを知るのに、あなたはこの靴を試す必要がある」
ーI recommend slipping them on, then you'll see how nice they feel.
「とにかく履いてみてください。そしたらどんなに履き心地が良いかわかります」
ご参考まで!