Let me preface this with: You don’t have to. Not everyone who is polytheist honors or worships deities. All it means to be a polytheist is to acknowledge they exist. You can do that without ever incorporating a deity into your life.
The first step to incorporating deities into your life is to get familiar with the deities, specifically the deities of Gaelic polytheism. To do this, you should start learning lore. Knowing the stories of the deities gives you some context of their character.
The next step is decide how intensely you want to incorporate deities in your life. The most passive level of incorporation would be recognition. Such as when a storm blows through your area and you think to yourself, “Must be Manánnan visiting!” Or thinking about the Morrígan when you encounter black birds.
Meanwhile, the most aggressive level of incorporation would be daily prayers to the deities and daily offerings. Leaving an offering for the An Cailleach Bhearra so that a winter storm passes quickly. Praying to Lugh daily to give you strength. Asking Brighid for help healing from a sickness.
You can of course be in the middle of these two extremes–I am! I often recognize deities in the environment around me, and think about them, but I rarely pray outside the entities I decided to build a relationship with.
Incorporating deities into your life will be a work in progress. Don’t try to rush everything at once. Maybe pick one deity to start learning about, and figure out if that is a deity you even want to incorporate in your life. If they are, then slowly incorporate one thing from that deity into your daily life. For example, let’s say you learn about goddess Brighid and decide you want to pray to her for all health concerns. Maybe you do a daily pray asking her to bless your health daily. Then, after you feel you got the hang of that, learn about Nuada and see what his lore can tell you about his character.
Again, it’s a work in progress. I’ve been a Gaelic polytheist for years and I still find new ways to incorporate deities into my life and religious practice. Go at your own pace and–most importantly–do what you are comfortable with.