I’m assuming you have a stellar wallet. If not, go get one from the official curated list of options here: https://www.stellar.org/lumens/wallets/
I’m going to keep this general since I don’t know what type of stellar wallet you have.
Let’s look at a sample widget:
Support. See the Stellar Address and Memo? From your web wallet, start a transaction; a request to send lumens to a destination.
Set the destination to the Stellar address listed and set the memo field to what the widgets lists under memo.
Easy? Awesome. If not, feel free to create an issue here: https://github.com/Toneco/Widget/issues.