Hello, Always Curious,Welcome and thanks for your question. You're embarking on a great hobby. When you reach the point where you originally began, make sure the stitching overlaps the original stitching. Some people put the machine in reverse, sew 4-5 stitches and then forward again. Then cut both threads and pull the tail of the thread on the front of the garment through to the back side and tie the two together. Just give a little tug on the back thread and it will loosen so the front end can be pulled through with a crochet hook or your fingers.
When I was a girl, I was taught to leave long tails at the end. Then when you pulled the front thread through to the back, you could thread a hand needle and tack the threads on the back side. That may seem like overkill, but you can be sure the threads weren't going to come apart at that spot.
I hope you are going to like sewing. Nothing fits as well as something you've made for yourself (unless you can afford to have clothes tailor-made) .
All the best,
I think I have the picture Let me know if I'm not understanding.
When you lower the presser foot onto the fabric where you want to begin, hold onto the bobbin thread and the tail of the top thread where they come out of the plate. Once the needle is lowered into the fabric to begin the first stitch, you can use these threads to gently ease the fabric through the feed dogs from front to back as you sew. Use your right hand on the wheel to slow the machine down so you are just making one or two stitches at a time. Once you are started with 5-6 stitches you can let the loose threads go and sew as usual.
Hope you are having fun!