To increase the WordPress allowed memory size for your website:
1) Open wp-config.php, which by default is located in the root WordPress directory.
Find the following line near the end of the file:
/* That’s all, stop editing! Happy blogging. */
Just above that line, add the following line:
Save your changes.
You can also increase memory to a higher number, and you can also increase the memory limit for admin tasks, as described in the WordPress codex.
If you’re still receiving the error after this fix, contact your web host provider or server administrator for their help.