Several sites say that it's the same as Facebook: "As soon as you use the # symble a blue box will appear over your tag. Then click Post. Your tag will appear in bold within your status update." . . but that doesn't work in Twitter. How can text in tweets be made boldface?
Use this tool: https://yaytext.com/bold-italic/ Just type in whatever text you want then tweet it. Note: your links are not going to be clickable if you pass them through the tool. If you want them to be clickable, you will have to add them before you submit the tweet.