I am a bitcoin newbie and I have created a so-called wallet, but I can't seem to find any instructions on how to actually put money into it so I can make bitcoin payments. Can anyone clear this up for me, please?
First of all, welcome
Second, make sure the wallet you're using is trustable... Don't use online wallets or exchange wallets. As a matter of fact, if you're holding a small amount of BTC, i'd recommand downloading electrum from the official site and verifying the signature.
If you don't mind waiting a couple of days and using a couple hundred gigs of diskspace, bitcoin core is also a very nice wallet.
If you'll be holding a lot of btc, move to a hardware wallet, paper wallet or airgapped wallet.
Now we have that out of the way, back to your question: you buy btc from an exchange or P2P (peer to peer) with FIAT (USD, EUR, SEK,...). From this exchange, you withdraw the funds to your wallet.
There's a whole subforum about exchanges: https://bitcointalk.org/index.php?board=223.160
P2P trades are usually done trough localbitcoins.
As a newbie, it's especially important to do your homework. You'll have to vet the wallet you're using and the exchange you're going to use to exchange fiat to BTC. Don't hesitate to ask help if you have troubles picking a wallet/exchange, and make sure you only take advice from people that know what they're talking about (there are alway people that are shilling for unknown exchanges, and scammers that try to push you to use their scammy wallets,... .So you'll have to review their trust feedback and rank before you even try to trust them.)