diff --git a/How-to-install.md b/How-to-install.md
index 30d74d2..d7ceb6e 100644
--- a/How-to-install.md
+++ b/How-to-install.md
@@ -1 +1,73 @@
-test
\ No newline at end of file
+Update the Linux/BSD system with latest CA bundle and patches from System Update otherwise some issues may occur when generating your free SSL certificates.
+Once completed begin with the install procedure below.
+- CentOs: `yum update ca-certificates`
+- Debian: `apt update ; apt install ca-certificates` (updates package if already installed) \
+  also applies to Debian-based distros like Ubuntu, LinuxMint, etc.
+
+## 1. Install from web: https://get.acme.sh
+
+Install https://github.com/acmesh-official/acme.sh
+
+```
+curl https://get.acme.sh | sh -s email=my@example.com
+```
+
+or
+
+```
+wget -O -  https://get.acme.sh | sh -s email=my@example.com
+```
+
+## 2. Or, install from GitHub:
+
+```
+curl https://raw.githubusercontent.com/acmesh-official/acme.sh/master/acme.sh | sh -s -- --install-online -m  my@example.com
+```
+
+or:
+```
+wget -O -  https://raw.githubusercontent.com/acmesh-official/acme.sh/master/acme.sh | sh -s -- --install-online -m  my@example.com
+```
+
+
+## 3. Or, git clone and install:
+
+```
+git clone --depth 1 https://github.com/acmesh-official/acme.sh.git
+cd acme.sh
+./acme.sh --install -m my@example.com
+```
+
+
+## 4. Advanced installation
+
+```
+git clone --depth 1 https://github.com/acmesh-official/acme.sh.git
+cd acme.sh
+./acme.sh --install  \
+--home ~/myacme \
+--config-home ~/myacme/data \
+--cert-home  ~/mycerts \
+--accountemail  "my@example.com" \
+--accountkey  ~/myaccount.key \
+--accountconf ~/myaccount.conf \
+--useragent  "this is my client."
+```
+
+You don't need to set them all, just set those ones you care about.
+
+Explanations :
+
+- `--home` is a customized dir to install `acme.sh` in. By default, it installs into `~/.acme.sh` 
+- `--config-home` is a writable folder, acme.sh will write all the files(including cert/keys, configs) there. By default, it's in `--home`
+- `--cert-home` is a customized dir to save the certs you issue. By default, it's saved in `--config-home`.
+- `--accountemail` is the email used to register an account to Let's Encrypt, you will receive a renewal notice email here.
+- `--accountkey` is the file saving your account private key. By default, it's saved in `--config-home`.
+- `--useragent`  is the user-agent header value used to send to Let's Encrypt.
+- `--nocron` install acme.sh without cronjob
+
+## 5. Special case: Converting LE account data from certbot to acme.sh
+If already using certbot, then there is the possiblity to convert its LE account data to acme.sh format.
+See https://github.com/maddes-b/linux-stuff/tree/main/acme.sh .
+
+If re-using the LE account created from certbot, then it is recommended **not** to specify `-m/--email` during installation.