How to search someone else's SMS number to send a message?

You mean how to find someone in the address book and send a text message? Details are as follows:

Different mobile phones should be different, but they are probably the same.

Click the SMS icon to enter the page. There is a+in the upper right corner. Click it. There is a recipient column at the top. There is a personal portrait icon on the right side of this column. Click it.

After clicking in, it will be a new address book, and you can find the person you want to send.