You should alredy know the answer to this.. you practice, and a lot! Eventually your fingers get used to the feeling of the keys and know where to go without looking, or with just a quick glance. Just try some very very easy songs where neither of your hands have to move. You can number the notes (like if you use your thumb it’s 1, pointer finger 2, etc). This helped me a lot. It isn’t easy, I play 5 instruments and piano is by far the hardest for me even though I started it first.

So in the end my suggestion is find a very simple song, preferably one that you are familiar with so you already know how long to hold the notes. If you still have trouble, number the notes. Play through the song for 3 days or until you have it memorized and can play without the music. Get a different song. Repeat. Ta da.

Well I never really had trouble playing the piano except that I got kinda bored of it but what I did to help me out was memorize. You say that you’re not that good with memory. But what you can do is instead of trying so hard to memorize the chords and the notes and all the stuff! Just make it simple and try to remember your hand movements. For me it worked really well. I really wasn’t all the good at reading the notes and I was slow at it so I couldn’t keep up. So just keep practicing and your hands will just move by themselves and will start to play. I dont mean that literally though. lol

Its Actually Practice That Helps Us to read the sheets and playing piano at the same time….now,what should you do is that you should develop your musical ear..that means that if any random key on the piano is played…you should be able to recognise the name of the key or atleast…fix the sounds of the keys in your mind…Now,dont just start playing the piano by looking in the sheet…you should first understand the sheet of the particular song….Observe the Ups and Downs in the Melodies of the song…then,dont play on the piano,but take a rough idea of that music in your mind…Then,when you’re done with it…play that on the piano…it will be very easy for you to play and see the sheet as you’ve already studied the sheet…you can easily capture 4-5 notes at a time and then continue to play like it….( In the beginning studying sheets would take some time but then,after some practice…you would be able to do that in 2-3 minutes…)

It is true that sight reading is difficult for every instrument and the amount of time it takes to master differs for each individual.
I remember when I first struggled with sight reading at the piano and thinking that I would never be able to do it.
I promise you it is just a matter of practising, and not just one particular piece you want to play, but all kinds of pieces. It is a good idea to begin sight reading easier, “beginner” pieces and there are many books of pieced designed for sight reading at different levels.
After practising a lot, you will find you can “feel” the places of the keys under your fingers and will be able to tell which note you’re playing without looking.
JUST PRACTISE