First off, good for you for learning to drive a stick. You will find it rewarding, especially in a 140.

Don't attempt to get it into first when moving at an "appreciable speed". The gearbox is just not designed for that. Nothing beats the hell out of a first gear syncro like sliding it into first while still moving. I'm not saying it can't or should never be done, it's just that it's pretty rough on the gearbox. If you're crawling, you may be able to get it in, but if you are moving at more than maybe 5 mph, use second gear. It will never slide into first as easy as the other gears when moving.

140s are geared so low, there's no problem chugging away from a crawl in second. Sometimes from a stop, and pointing downhill, you can skip first altogether.