Tips for Getting Started
Have a designated space for doing activities with your child.
This doesn't have to be a whole room, or a new piece of furniture. This can be an existing table, a new table cloth you throw on the table to signal it's function, a rug on the floor, etc. If your child is able to easily communicate when they want to do things with you, this may not be a big deal. However, for kids who can't, this gives them a means of saying "I want to do something with you" without needing the words.
Channel your inner children's program host.
Think of Ms. Rachel, Mr. Rogers, etc. These highly successful children's educational entertainers use calm and cheerful voices. Mr. Rogers is rather mellow, while Ms. Rachel has quite a bit of energy in her voice. They each have different styles, so find your personal fit using them as guides for opposite ends of the range you want to hit.
Start with an activity that is closest to their skills and interests.
If your kid loves books, jumping straight into a book is fine. If your kid speaks in phrases or short sentences, starting with the book is probably fine. If your kid is using single words, especially with visual cues, and isn't into books, you might want to start with individual pictures first. You can use the bingo draw cards as flashcards - but unless your child enjoys flashcard drills, don't employ those. Simply present 1 at a time to your child, telling your child what each one is. If your child doesn't want to accept them, then adapt to that. Most likely they will either already know what each picture is, or they will want you to tell them soon. Let your child play with them as they choose. If they start handing them to you, they are likely wanting you to name them, so play along!
Eliminate words like 'wrong' from your vocabulary.
The last thing we want to do is to discourage our children from trying. You can model the correct way. You can ask them "Hmm, does that match?" with the most genuine, non-judgemental tone. We use "So silly! That's not a ....." which my son LOVES. He giggles and smiles so big every time. "Wrong" is quite condemning. We're having fun! There's no wrong answers, just great and silly answers. Find the words that your child responds to best to denote the need to try again. If you can't, don't even worry about it. "Great try!" and "Nice effort!" spoken with the same tone you'd use had they gotten it correct can really help build their confidence.
Introduce only 1 activity a day, 2-3 times a week (unless they ask for more!)
Part of the low pressure aspect of this is not making these sets a chore. I like to introduce 1 activity a day, every other other day. I make the books available all the time for my child to use whenever he wishes. Sometimes he just plays with the velcro cards. That's fine. We'll read that book for a couple of days, then bring out a new activity. Try and be with your child to do the activities with them as much as they'll allow, narrating them for them. You are modeling using the words in different ways when you do this. Hope that they will repeat you, but don't tell them to. They will when their brain is ready. I never take books or reusable activities away unless they are destroyed.
Finally, don't give up if your child gets part way through a book and closes it or walks away.
My own son did this several times. Then he'd bring it back a few hours later, or the following day. I suspected that he wasn't used to having books and activities designed for his language acquisition type, and it was so new to him that it was just a bit overwhelming. I followed his lead - reading with him when he wanted to, and he soon began to say the words with me. Before I knew it we were reading the entire book and running out of activities. Then he was asking for "another one book!" Honor your child's attempt to stop, but don't give up on it right away. Give your child time to process it all. It could take days or even weeks for a child to be ready, and that is just fine.