Time...

Hello Guest we really need more information from you? But they will grow at different speeds depending what they are? The dominant ones may take light, water and food from the slow growing ones and slow them even more possibly even kill some depending how close you have planted them?

Careful application of fertilizer can also help, especially if they are in poor sandy soil, or in containers. Most conifers prefer a slow-acting organic feed applied in spring, if needed, and in mid summer, for some species. Also for those in containers, be sure to change up to a larger container in a timely manner--the faster growing ones will need to be bumped up 10 cm every year, while miniatures will only need 5 cm every other, or every third year, for maximum growth rate. Changing up to a much larger pot may be counterproductive, since all that unused soggy compost is an open invitation to root rot. For those in the ground, as Drc726 says, proper spacing is critical: I would read up on the mature size of each variety.