You can start showing your older child books and shows with children. You can tell him about how he was when he was a baby, wore diapers, sat in a high chair, couldn't walk yet, couldn't bathe himself, needed help sitting up, put everything in sight in his mouth. Talk about all the things he used to do.
You can involve him in helping baby brother grow up. He can help feed him, hold the bottle, get the diaper bag or changing items, play with baby with toys. In the beginning, baby will take a lot of time because of nursing. However, I would feed bottles to my child and sit on the couch. I could play with the other one at the same time. I moved the high chair into the living room, so I could watch my older child. Sometimes I moved a few of my older child's favorite toys to the kitchen while I fed the younger.
You can start playing learning games with the older one while you are feeding the baby. I play a game I made up called "Blues Clues". It's basically the same theory as "I Spy". I tell my child to find a color, shape, number, an item beinning with a letter or sound, etc. You can put whatever theory behind it you want. You can make it a special time for all of you.
I think it's important to teach littles ones how to play together, look out for each other and have individual time. I set time out for just my older son and just my younger son. I read books to my older son while the other plays with his toys or looks at pictures. Sometimes we sing together, go to the store, work on school things like writing or learning letters. You can show the older child there are things the younger cannot do yet, and make those times feel special to him. He can stay up later. He can eat new foods. He can play on different equipment at the park, play putt-putt golf, go bowling, etc. I get my younger son to be excited about the new things that the older can do and vice versa. My older son is excited to teach his younger brother how to write, learn numbers, play a game, etc. They are both really excited together about playing and learning.
It can feel overwhelming to bring home a new baby, but it make take some scheduling. Think about the time it takes to do laundry, clean the house, feed baby and change him, making meals, naps, etc. You can find time that baby is sleeping to play with the older sibling alone. There are so many new and exciting things that the older sibling has yet to experience and learn that he doesn't have to feel left out. Give him things to look forward to, goals, inspiration, activities, time with just Dad or just Mom. He will be just as excited to have a new baby in the house as you are.