Soil tests performed by soil-testing laboratories usually include instructions for how much lime to apply (often per 1,000 square feet) to adjust pH to a certain level. Home testing kits may not provide results that are accurate enough, though the precision of a 4.6 measurement suggests this was a lab result. (If your test was not through a laboratory, having one performed is a good idea and will provide more useful information.) Lime dosages not only depend on starting pH, but also on soil type. If not provided by the lab, you can look on the label of lime products (probably on the back of the bag) for a chart or written guide to volume to use for a given area and with a known starting-point pH and desired ending-point pH. Here is a bit of lime info, though geared in this case towards lawn applications, as that is often the only yard area which needs adjustment: https://extension.umd.edu/resource/lime-and-lawns
Also, see the "soil pH" section of this page for more information and guidelines on liming soil: https://extension.umd.edu/resource/soil-testing-and-soil-testing-labs

While tolerances may vary by species and reference cited, Serviceberry (of which there are multiple species) and Buttonbush both grow just fine in pH levels down to about 5.0 or 5.5. American Hazelnut is listed as both circumneutral and tolerant of a wide range of pH, including acid (below 6.0, but not otherwise specified). Therefore, minimal adjustment, if any, would be needed to have the plants grow satisfactorily. pH changes to soil tend to be (and should be) gradual, but you can probably plant now and have them start establishing, working on making slow changes over time. (Lawns, for example, are also be limed "in-progress" instead of waiting for optimal conditions before seeding.) The roots will grow best where the pH and other factors (nutrient load, moisture retention, oxygen availability) suit them best, so you do not need to worry about the pH of deeper layers.

Miri