Trust in accumulation is a phrase I say to remind myself to have patience and faith when I begin an endeavor that is going to take a long time before I see the fruits of my labor. By steadily and diligently working eventually my efforts accumulate, and I accomplish what I set out to do.
Becoming fluent in a foreign language is like this. People of all ages can learn a foreign language, but they need to have patience and know that it usually takes years, depending on their circumstances. Sometimes a person is lucky and is immersed in the foreign language by living in a place where it is spoken or attending school where it is used all day everyday. Then the learning goes more quickly. But, in most cases people are learning the foreign language while living at home.
So, what is important is to get started and steadily work on reaching your goal over time. For elementary and middle school students, I tell parents, "Time is on your side!" Often, parents' goals are that their children become fluent by the time they are adults, in which case they have lots of time for their children to work toward that goal.
Knowing this, parents can relax and implement language learning on a steady basis in reasonable amounts of time. What is important is the continuity.
Parents, or anyone, may ask, "How often should we work on it?". Well, this depends on what you can manage. You can choose to work one hour 3 times a week, 15 minutes 3 times a week, 1/2 hour 4 times a week, 1 hour twice a week, etc. The key is to try something and keep it going. Adjust as needed, but keep feeding it so it grows!
And, at some point enroll in a class where you can practice conversation, or find a Spanish speaker to help with this. Speaking is the most difficult piece of becoming fluent.
And then, trust in accumulation. Over time your efforts will accumulate, and you will see that you have something of substance and value. Then, keep going, so that one day you become fluent!