18.04 has been out for less than a week. As such, many developers haven't caught up to the new release yet. To that end, WineHQ has a bug for this already requesting 18.04 packaging in their repository.
There is Wine 3.0 in the Ubuntu repositories, you can use that in the interim by executing
sudo apt install wine. Once the upstream WineHQ repositories catch up you can use them.
Once that time is available, you can follow the instructions for installing from their repos. From their instructions page are the instructions to follow at that time:
If you have previously installed a Wine package from another repository, please remove it and any packages that depend on it (e.g.,
wine-mono, wine-gecko, winetricks) before attempting to install the
WineHQ packages, as they may cause dependency conflicts.
If your system is 64 bit, enable 32 bit architecture (if you haven't
sudo dpkg --add-architecture i386
Add the repository:
wget -nc https://dl.winehq.org/wine-builds/Release.key
sudo apt-key add Release.key
sudo apt-add-repository https://dl.winehq.org/wine-builds/ubuntu/
sudo apt-get update
Then install one of the following packages:
sudo apt-get install --install-recommends winehq-stable
sudo apt-get install --install-recommends winehq-devel
sudo apt-get install --install-recommends winehq-staging
If apt-get complains about missing dependencies, install them, then repeat the last two steps (update and install).
Staging isn't really used anymore, so use either Stable or Devel.
There will be differences though:
Files are installed to
Menu items are not created for Wine's builtin programs (
winecfg, etc.), and if you are upgrading from a distro package that had added
them, they will be removed. You can recreate them yourself using your
Binfmt_misc registration is not added. Consult your distro's documentation for
if you wish to do this manually.
WineHQ does not at present package
wine-mono. When creating a new wine prefix, you will be asked if you want to download
those components. For best compatibility, it is recommended to click
Yes here. If the download doesn't work for you, please follow the
instructions on the Gecko and
Mono wiki pages to install them