The next step is to have a decent printer to proof your files. Make sure you have the correct profile for the paper you are printing on. It does not have to be the same paper we would be using for the final work but it needs to be a good quality paper.
There will be necessary adjustments to make to the scan. No scan comes out matching the original. Photoshop is pretty much a must to achieve good results. There are free alternatives to Photoshop, such as GIMP.
Both programs have histogram analysis of each image. In Photoshop they are called levels. Levels constrol brightness and saturation. A giclee print will not properly match the original if histograms are not correct. Therefore make sure there is no flat space at the left or right of the histogram. If there is, move the cursors in to the origins. Once you adjusted levels, it is time to do color. Color can be corrected by visually matching the original to what is seen on the the calibrated screen. The tools are all in these programs. Curves, levels, hue and saturation are among some of the best. Any color cast can be corrected in RGB. There are times, more often than not, where individual masking (selection of an individual area) is required. The reason is that some pigments do not react to scanners the same way and they have to be corrected away from the rest.
The last step is to verify your corrections by printing a proof on your own printer. Again, make sure your printing software has the correct paper profile loaded.