Welcome to the forum.
With digital photography, it's is very helpful to develop a 'work flow' for your digital images.
Obviously, you use the camera to create the photos. Then you should get the files from your memory card onto your computer (either by connecting the camera to the computer or taking the card out and using a card reader).
Once you have the images on your computer, you should have some software that will allow you to look at the images and make adjustments if you like. The camera will have come with software for this but there are many options (Photoshop and such).
Here is where you can choose the images that you want and make adjustment, maybe crop or rotate them...even apply special effect if you want to.
Then you should save your edited images (probably best to 'save as', so that you don't overwrite the original files).
If you haven't resized them or copped too much, there should be plenty of resolution for whatever print size you need.
You should then be able to upload these files to an on-line print service, or you could put them on a disk or thumb drive and take then into a lab (most labs probably have a self serve kiosk for this).
A lot of people have steps where we back-up the original files. Many of us shoot in 'RAW' mode, which requires that we use software to convert the RAW files at some point in the workflow. The point is that you should figure out a 'work flow' that works for you.