“Having faith” is a skill. Like any skill, it can be learned, however gradually. Some master it more quickly and fully; some less so. All can make progress in developing it.
How can we learn to “have Faith”? It helps to have a clear definition of the skill we’re trying to master. We know what “piano playing” is. If we want to develop that skill, we know — at least in a general way — what to do: get a piano and start exercising our fingers!
“Faith” isn’t a physical object like a piano, but it’s a skill with a definable content and method.
What, then, is “having faith”?
Faith, according to Rabbi Morris Lichtenstein, is the “whole-hearted realization of the Divine Presence, accompanied by the conviction of His profound Goodness.” 
Both parts — “realization” and “conviction” — refer to our thinking; to something we do. The practice of having Faith, then, begins with choosing our thoughts. “Choosing” thoughts means giving more attention to some than to others.
We might begin by developing the realization of the presence of G-d (even if not whole-hearted at first). There are many paths to this. There are many teachers, each of whom goes about this in a different – but no less valid – way. Many begin by giving us Divine qualities to “consider” (which, in its deeper phases, means “contemplate”): Rabbi Lichtenstein, for example, gives us Unity, Omnipresence, Creativeness, Goodness, and Responsiveness to Prayer, among others. Rabbenu Bachya gives us his recommendations in “Duties of the Heart”; the poem/hymn “Adon Olam” gives others, still; etc. When we’ve learned to “consider” any one list, we’ll find that “considering” any other list comes all the more easily. But a fundamental idea that underlies them all is that there is no power and no presence separate from or other than G-d. The belief in any other power or presence is itself the error by which we hide G-d from ourselves.
How do we change that error?
Strangely, we can’t force ourselves to think differently. Rather, we can introduce an idea into our thinking — “Unity,” for example. We can try to understand uncritically, but with gradually increasing clarity, what Rabbi Lichtenstein means by it. We might re-read it each day, or every now and then. We might review or repeat it in our minds; keep it fresh in our thinking. We need not expend any more conscious effort than is comfortable for us.
Somewhere in the process, though, something surprising happens: our viewpoint suddenly changes. At first, it might be an “ah ha” moment — a sudden sense of new understanding or insight into what the idea has to do with us individually and personally. It’s not an “intellectual” realization; better, it’s not an “intellectualized” one. It’s a shift in our thinking. “ChaBaD” seems to describe the same process: “Chochmah” is the introduction of the broad concept; “Binah” is the working out of the details in our thinking; “Da’at” is that moment where it changes us spontaneously and forever. Our “consideration” will be made up of many such moments which, cumulatively, develop our “faith.” Sometimes, these moments will even be accompanied by a simultaneous and equally spontaneous burst of joy within us.
But even an “ah-ha” moment isn’t essential. The real change is gradual, and over time.
As we do this practice at our leisure, and are changed by it, we simultaneously receive an added, unexpected benefit: we can use it to call on our faith in those times of difficulty, when we do, in fact, need to “have faith.”