Created Issue a cert from existing CSR (markdown)

Issue-a-cert-from-existing-CSR.md

@@ -0,0 +1,39 @@
+From v2.4.4, acme.sh support to issue a cert from an existing csr.
+
+There are 2 commands related:
+
+1. Display the content of the csr:
+
+```
+acme.sh  --showcsr  --csr  /path/to/mycsr.csr
+```
+
+It shows the subject and domain names in the csr.
+
+2. Issue a cert from the csr.
+
+```
+acme.sh  --signcsr   --csr  /path/to/mycsr.csr  -w /path/to/webroot/
+```
+
+The first parameter is the csr file,  all the other parameters are same as `--issue` command.
+
+For exmaple,  you can specify the sepearate  webroot folders for each domain in the csr.
+
+```
+acme.sh  --signcsr  --csr  /path/to/mycsr/csr  -w /wwwroot/aa.com  -w /wwwroot/www.aa.com  -w /wwwroot/bb.com
+```
+
+Another example, use dns mode:
+
+```
+acme.sh  --signcsr  --csr /path/to/mycsr/csr  --dns  dns_cf
+```
+
+
+The parameters are same as `--issue` command.
+
+See : https://github.com/Neilpang/acme.sh/wiki/How-to-issue-a-cert
+
+
+