You can share files in Google Drive, but in some instances you may want to email files as an attachment. It is easy to compress those files and create an attachment using Google Drive, no matter where those files are originally located.
You need to first get your files into Google Drive.
Launch Google Drive.
Browse to the location where you want to upload your files. (You can create a new folder for them if you want.)
On the upper left, click on the + New button.
Select File upload from the menu.
From the files on your computer, browse to the location of the file or files you want to upload.
Select the file (or files, using Ctrl to select multiple files) and press the open button on the bottom right of the window.
You will get a Google Drive message saying it is uploading the item/items. When it is finished it will say "Upload complete" or "Uploads complete".
Repeat steps 3-7 until you have uploaded all the files you want to send as an attachment.
After all your desired files are in Google Drive, select the files for download.
Hold down the Ctrl key and select all the files you want to email/compress.
At the top right of the Google Drive window, select the icon with three vertical dots. (Note that this icon will only appear after you have selected one or more items.)
Select Download from the menu.
Google Drive will compress (or zip) all the files you selected and start the download process.
Once the files have finished compressing and downloading, you will see the .zip file listed in the bottom left of your browser.
Click the up arrow to open the menu and select Show in folder.
Most likely this file will be in your Downloads folder. This is the file you will want to attach to your email.