I tied my shoelaces tightly so they wouldn't come loose.
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means bind, so the verb version is to tie or to bind.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You haven't learned this reading yet, so here's a mnemonic to help you:
What do you want to tie up? Your Shiba (しば) Inu! She's always running off and getting into trouble. You have to tie her up outside when you leave the house. It's sad, but at least it keeps her safe!