Setup

Here is how to install zsh with a custom theme and some basic plugins.

Install zsh with the package manager of your choice
Install ohmyzsh with 

sh -c "$(wget -O- https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

Install the powerlevel10k theme with 

git clone --depth=1 https://github.com/romkatv/powerlevel10k.git ${ZSH_CUSTOM:-$HOME/.oh-my-zsh/custom}/themes/powerlevel10k

Set ZSH_THEME="powerlevel10k/powerlevel10k" in ~/.zshrc
Restart your terminal or use the command

p10k configure

Go through the configuration and customize it to your liking
In this guide we will install history-substring-search, zsh-syntax-highlighting and zsh-autocomplete

git clone https://github.com/zsh-users/zsh-history-substring-search ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-history-substring-search

git clone https://github.com/zsh-users/zsh-syntax-highlighting.git ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-syntax-highlighting

git clone https://github.com/zsh-users/zsh-autosuggestions ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-autosuggestions

When all of them are downloaded you will need to activate them, you do that by adding their names to the plugins section in your ~/.zshrc
This is how it can look like

plugins=(
    git
    history-substring-search
    zsh-syntax-highlighting
    zsh-autosuggestions
)

Git was preinstalled when we installed ohmyzsh
To use the plugins now you will need to type source ~/.zshrc or restart your terminal
Now you have a working install of zsh with plugins and a theme 🚀

For an even better experience I would recommend that you try out the Meslo nerd font for powerlevel10k
How to install that is highly depended on your distro, but on arch it is available in the aur